PHYSIOLOGICAL REVIEWS
Vol. 81, No. 1, January 2001
Printed in U.S.A.
Magnesium Transport in the Renal Distal Convoluted Tubule
LONG-JUN DAI, GORDON RITCHIE, DIRK KERSTAN, HYUNG SUB KANG, DAVID E. C. COLE,
AND GARY A. QUAMME
Department of Medicine, University of British Columbia, Vancouver, British Columbia; and Department of
Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
I. Introduction: Importance of the Distal Convoluted Tubule in Renal Magnesium Balance
II. General Characteristics of Magnesium Absorption in the Distal Tubule
III. Magnesium Uptake in Isolated Distal Cells
A. Measurement of cellular Mg2⫹ transport
B. Dependence of cellular Mg2⫹ uptake on membrane voltage
C. Schematic model of distal cellular Mg2⫹ transport
IV. Load Dependence of Magnesium Absorption in the Distal Tubule
V. Hormonal Control of Magnesium Transport in the Distal Convoluted Tubule
A. Peptide hormones
B. Steroid hormones
C. Prostaglandins
D. Insulin
E. Other hormones and factors
F. Hormonal regulation and renal Mg2⫹ handling
VI. Extracellular Calcium/Magnesium-Sensing Receptors in the Distal Convoluted Tubule
A. Ca2⫹/Mg2⫹ sensing modulates peptide hormone responses at the receptor level
B. Ca2⫹/Mg2⫹ sensing modulates steroid hormone responses at the transcriptional level
C. Ca2⫹/Mg2⫹ sensing modulates other hormone responses
VII. Intrinsic Control of Magnesium Transport in the Distal Convoluted Tubule
VIII. Distal Diuretics That Enhance Magnesium Absorption in the Distal Convoluted Tubule
A. Amiloride
B. Chorothiazide
IX. Familial Disorders Affecting Distal Magnesium Transport
A. Hypomagnesemia associated with abnormal renal NaCl transport
B. Inherited disorders associated with abnormal extracellular Mg2⫹/Ca2⫹ sensing
C. Primary inherited disorders of distal Mg2⫹ transport
X. Acquired Disorders That Diminish Distal Magnesium Transport
A. Potassium depletion
B. Phosphate depletion
C. Acid-base changes
D. Cytotoxic agents
XI. Summary: Future Directions in Research of Magnesium Transport in the Distal Convoluted Tubule
52
52
53
53
54
54
55
56
56
59
61
62
62
63
63
65
66
66
67
67
67
68
68
69
71
72
73
73
73
74
74
76
Dai, Long-Jun, Gordon Ritchie, Dirk Kerstan, Hyung Sub Kang, David E. C. Cole, and Gary A. Quamme.
Magnesium Transport in the Renal Distal Convoluted Tubule. Physiol Rev 81: 51– 84, 2001.—The distal tubule
reabsorbs ⬃10% of the filtered Mg2⫹, but this is 70 – 80% of that delivered from the loop of Henle. Because there is
little Mg2⫹ reabsorption beyond the distal tubule, this segment plays an important role in determining the final
urinary excretion. The distal convoluted segment (DCT) is characterized by a negative luminal voltage and high
intercellular resistance so that Mg2⫹ reabsorption is transcellular and active. This review discusses recent evidence
for selective and sensitive control of Mg2⫹ transport in the DCT and emphasizes the importance of this control in
normal and abnormal renal Mg2⫹ conservation. Normally, Mg2⫹ absorption is load dependent in the distal tubule,
whether delivery is altered by increasing luminal Mg2⫹ concentration or increasing the flow rate into the DCT. With
the use of microfluorescent studies with an established mouse distal convoluted tubule (MDCT) cell line, it was
shown that Mg2⫹ uptake was concentration and voltage dependent. Peptide hormones such as parathyroid hormone,
calcitonin, glucagon, and arginine vasopressin enhance Mg2⫹ absorption in the distal tubule and stimulate Mg2⫹
uptake into MDCT cells. Prostaglandin E2 and isoproterenol increase Mg2⫹ entry into MDCT cells. The current
http://physrev.physiology.org
0031-9333/01 $15.00 Copyright © 2001 the American Physiological Society
51
52
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
Volume 81
evidence indicates that cAMP-dependent protein kinase A, phospholipase C, and protein kinase C signaling pathways
are involved in these responses. Steroid hormones have significant effects on distal Mg2⫹ transport. Aldosterone
does not alter basal Mg2⫹ uptake but potentiates hormone-stimulated Mg2⫹ entry in MDCT cells by increasing
hormone-mediated cAMP formation. 1,25-Dihydroxyvitamin D3, on the other hand, stimulates basal Mg2⫹ uptake.
Elevation of plasma Mg2⫹ or Ca2⫹ inhibits hormone-stimulated cAMP accumulation and Mg2⫹ uptake in MDCT cells
through activation of extracellular Ca2⫹/Mg2⫹-sensing mechanisms. Mg2⫹ restriction selectively increases Mg2⫹
uptake with no effect on Ca2⫹ absorption. This intrinsic cellular adaptation provides the sensitive and selective
control of distal Mg2⫹ transport. The distally acting diuretics amiloride and chlorothiazide stimulate Mg2⫹ uptake in
MDCT cells acting through changes in membrane voltage. A number of familial and acquired disorders have been
described that emphasize the diversity of cellular controls affecting renal Mg2⫹ balance. Although it is clear that
many influences affect Mg2⫹ transport within the DCT, the transport processes have not been identified.
1
The definitions used in this review are those proposed by the
Renal Commission of the International Union of Physiological Sciences
(170). The distal tubule is used to denote the nephron segment between
the region of the macula densa and the confluence with another tubule
to form a collecting duct. The distal tubule of micropuncture literature
comprises primarily the distal convoluted tubule and connecting tubule
(263). The distal convoluted tubule is restricted to the the cells comprising the DCT only.
Control of total body magnesium homeostasis principally resides within the nephron segments of the kidney.
The proximal tubule reabsorbs 5–15%, the thick ascending
limb of the loop of Henle absorbs 70 – 80%, and the distal
tubule reclaims some 5–10% of the filtered magnesium.
Although the distal tubule reabsorbs only 10% of the
magnesium filtered through the glomerulus, this amount
is significant because it represents 60 –70% of the magnesium delivered to this segment from the loop of Henle.
Because there is little magnesium reabsorption beyond
the distal tubule in the collecting ducts, the tubule segments comprising this portion of the nephron play an
important role in determining the final urinary excretion
of magnesium. The purpose of this review is threefold: 1)
to convince the reader that the distal tubule plays an
important role in controlling renal magnesium conservation (as important as the thick ascending limb); 2) to
discuss recent observations on how magnesium is reabsorbed and what controls magnesium transport within the
distal tubule; and 3) to indicate some of the unresolved
issues that require further investigation. Most of the recent studies involve the use of isolated cell lines which,
on balance, represent the intact distal convoluted tubule
(DCT).
II. GENERAL CHARACTERISTICS OF
MAGNESIUM ABSORPTION IN THE
DISTAL TUBULE
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
Most of our early knowledge concerning magnesium
transport in the distal tubule has come from micropuncture and microperfusion studies of the superficial
nephron (48, 131, 249, 251, 256, 288, 289, 344).1 Mi-
cropuncture studies showed that significant amounts of
magnesium are absorbed in the distal tubule (19, 92, 93,
248, 252, 254). The mammalian distal tubule, located between the macula densa and the cortical collecting duct
(CCD), comprises a short post-macula densa segment of
thick ascending limb, the DCT, the connecting tubule
(CNT), and the initial collecting tubule (333). The micropuncture studies describing distal magnesium absorption may well have included portions of the superficial
CNT as well as the DCT. R. J. M. Bindels failed to detect
any apical-to-basolateral (absorption) or basolateral-toapical (secretion) magnesium movement in a mixture of
rabbit CNT and CCD cells (personal communication).
However, there are significant functional differences
among the species and segments studied. There is a gradual transition between the DCT and CNT in human and
rats, whereas there is a sharp transition in the rabbit
(216). In the rat and human, chlorothiazide-sensitive NaCl
cotransport and parathyroid hormone (PTH)-stimulated
calcium transport occurs within DCT segments and PTHresponsive Na⫹/Ca2⫹ exchange within the CNT (226).
This is in contrast to the rabbit, where thiazide-sensitive
NaCl cotransport is found in the DCT but PTH-responsive
Na⫹/Ca2⫹ exchange is expressed only by CNT cells (10,
32, 264, 329, 330). The mouse appears to be more like the
rat and human because the two transporters are colocalized to DCT cells (108). Again, the species and segmental
differences of magnesium transport have not been studied.
Although significant magnesium reabsorption takes
place along the distal tubule, this is normally achieved
with little change in tubular magnesium concentration.
Luminal magnesium concentration may increase along
the distal tubule with increased magnesium delivery, or it
may decrease with magnesium restriction (92, 131, 248,
298). Normally, distal magnesium absorption is fractionally less than that of sodium or calcium (254). This is
I. INTRODUCTION: IMPORTANCE OF THE
DISTAL CONVOLUTED TUBULE IN RENAL
MAGNESIUM BALANCE
DISTAL TUBULE MAGNESIUM TRANSPORT
January 2001
53
III. MAGNESIUM UPTAKE IN ISOLATED
DISTAL CELLS
In vivo micropuncture and microperfusion approaches do not allow for study of cellular mechanisms,
and in vitro microperfusion studies have not been performed on DCT because of the difficulty in isolating intact
segments. Accordingly, isolated immortalized cell lines
have been used to study segmental responses.
2ⴙ
A. Measurement of Cellular Mg
Transport
We have used an established cell line representing
the DCT to study Mg2⫹ transport. This cell line (designated MDCT for mouse distal convoluted tubules) was originally isolated from mouse distal tubules and immortalized by Pizzonia et al. (238). Friedman and Gesek (111,
115–118) have shown that this cell line exhibits many of
the functional properties characteristic of the intact DCT
studied in vivo, such as amiloride-inhibitable Na⫹ transport, chlorothiazide-sensitive NaCl cotransport, and PTHand calcitonin-stimulated Ca2⫹ transport. Accordingly,
MDCT cells appear to have many of the properties of the
convoluted segment of the intact distal tubule.
Electrolyte transport is usually quantitated by isotopic flux measurements, but an appropriate isotope for
Mg2⫹ is not available (28Mg has a half-life of 21 h). Accordingly, we developed a cell model to assess Mg2⫹
transport using fluorescent determinations of intracellular free Mg2⫹ concentration ([Mg2⫹]i) (75, 253). Cytosolic
free Mg2⫹ concentration of epithelial cells is on the order
of 0.5 mM. This is ⬃1–2% of the total magnesium, the
remainder being complexed to various organic and inorganic ligands and chelated within the mitochondria. Using
isolated distal cell lines, we have shown that magnesium
entry is through specific and regulated magnesium pathways (76, 254). To determine Mg2⫹ transport, the epithe-
2⫹
FIG. 1. Intracellular free Mg
concentration ([Mg2⫹]i) in normal
and Mg2⫹-depleted immortalized mouse distal convoluted tubule
(MDCT) cells. Confluent MDCT cells were cultured in either normal (0.6
mM Mg2⫹) or Mg2⫹-free media (⬍0.01 mM) for 16 h. Fluorescence
studies were performed in buffer solutions in the absence of extracellular Mg2⫹, and where indicated, MgCl2 (5.0 mM final concentration) was
added to observe changes in [Mg2⫹]i. The buffer solutions contained (in
mM) 145 NaCl, 4.0 KCl, 0.8 K2HPO4, 0.2 KH2PO4, 1.0 CaCl2, 5.0 glucose,
and 10 HEPES/Tris, pH 7.4, with and without 5.0 mM MgCl2. The rate of
rise in intracellular Mg2⫹ concentration, d([Mg2⫹]i)/dt, is a reflection of
the entry rate of Mg2⫹ into the cell. Fluorescence was measured at 1 data
point/s with 25-point signal averaging, and the tracing was smoothed
according to methods previously described. [Data from Dai et al. (76).]
lial cells were first depleted of Mg2⫹ by incubating in
magnesium-free culture media. Subsequently, the cells
were placed in solutions containing magnesium and
[Mg2⫹]i measured as a function of time (Fig. 1). [Mg2⫹]i
increased until it had reached normal levels. The rate of
concentration change {d([Mg2⫹]i)/dt} is an estimate of
Mg2⫹ uptake rate. Influx of Mg2⫹ is concentration dependent so that the rate of Mg2⫹ transport increases with
external Mg2⫹ until saturation is attained (70, 76, 253).
Mg2⫹ influx into Mg2⫹-depleted cells was inhibited by
Mn2⫹ and La3⫹ and by dihydropyridine channel blockers
such as nifedipine. Ca2⫹ neither blocked Mg2⫹ entry nor
was 45Ca uptake changed in the presence of Mg2⫹ depletion or the Mg2⫹-refill process. These observations suggest that the influx pathway is specific for Mg2⫹ and not
shared by Ca2⫹ (76, 253). We used this approach to characterize the cellular mechanisms of Mg2⫹ uptake in MDCT
cells that may shed light on magnesium transport in distal
tubule cells.
Many hormonal and nonhormonal factors influence
2⫹
Mg uptake into MDCT cells. Our observations using
MDCT cells closely resemble earlier results using micropuncture and microperfusion techniques in intact rat
and dog distal tubules (Table 1). However, little is known
about the cellular mechanisms of electrolyte absorption
in the DCT from in vivo micropuncture and microperfusion experiments. Accordingly, the use of isolated cells
has allowed a greater in-depth study of cellular mecha-
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
commensurate with the fractional urinary excretion of
magnesium, normally ⬃3%, whereas the fractional excretion of sodium and calcium is ⬍1% (250). The evidence is
that net distal magnesium reabsorption is essentially unidirectional because no secretion of magnesium into the
lumen has been reported (254). Because the distal tubule
is characterized by a negative transepithelial voltage and
a high epithelial resistance, it is concluded that magnesium transport is active and transcellular in nature (165,
289). This is unlike magnesium transport within the thick
ascending limb that occurs passively through the paracellular pathway (249, 289). Although the micropuncture and
microperfusion studies have clearly shown that magnesium is reabsorbed in the superficial distal tubule, little
knowledge has been gained concerning the cellular mechanisms of magnesium transport.
54
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
1. Controls of magnesium reabsorption in intact
distal tubules compared with MDCT cells
TABLE
Intact Distal Tubules
Increase
Increase
Increase
Increase
?
(19)
(92, 243)
(19)
(93)
Increase
Increase
Increase
Increase
Increase
(68)
(UP)
(67)
(67)
(UP)
?
?
?
?
Increase (252, 298)
Decrease (298)
Increase (298)
Decrease (177, 254)
Decrease (178, 246)
Decrease (347)
?
Increase (69)
Increase (68)
Increase (75)
Increase (68)
Increase (76)
Decrease (72)
Increase (72)
Decrease (20)
Decrease (20)
Decrease (71)
Decrease (70)
No effect (254)
?
Increase (257)
No effect (76)
Increase (76)
Increase (70)
Results of the intact distal tubule were obtained using micropuncture and microperfusion studies. ?, Not known; UP, unpublished observations; MDCT, mouse distal convoluted tubule cell line; 1,25(OH2)D3,
1,25-dihydroxyvitamin D3.
voltage is normally in the range of 0 to ⫺30 mV lumen
negative, magnesium absorption is active in nature. Distal
magnesium absorption is entirely transcellular moving
across the DCT cell. Magnesium may move passively into
the cell across the luminal membrane driven by a favorable transmembrane voltage. The luminal magnesium
concentration is on the order of 0.2– 0.7 mM depending on
the condition studied, and intracellular free Mg2⫹ is 0.5
mM so that under some circumstances Mg2⫹ entry is
against an appreciable concentration gradient (76, 253).
We speculate that Mg2⫹ entry is through a unique channel,
and this transport is dependent on the transmembrane
voltage. The active step in transcellular movement is predicted to be at the basolateral membrane where Mg2⫹
leaves the cell against both electrical and concentration
gradients. The means by which Mg2⫹ actively moves
across the basolateral membrane is unknown. Evidence
taken from studies using nonepithelial cells suggest that
Na⫹/Mg2⫹ exchange may occur, Na⫹ moving back into
the cell coupled with Mg2⫹ exit from the cell into the
interstitium (126). Alternatively, a specific energy-dependent Mg2⫹ pump may be present analogous to that reported for calcium. Intracellular Mg2⫹ plays an important
role in enzyme functions including the transport ATPases
(102, 250). The ionic transport pumps such as Na⫹-K⫹ATPase, Ca2⫹-ATPase, and H⫹-ATPase require Mg2⫹ for
activity; accordingly, they are Mg2⫹-dependent ATPases
nisms of these hormonal and nonhormonal influences.
The similarity of results between the MDCT cell studies
and the micropuncture experiments support the use of
this cell line in characterizing cellular mechanisms of
Mg2⫹ transport.
B. Dependence of Cellular Mg2ⴙ Uptake
on Membrane Voltage
Our initial studies looked at the changes in Mg2⫹
entry into MDCT cells following alterations in membrane
voltage (76). In these studies, with the same starting
[Mg2⫹]i and the same external Mg2⫹ concentration, the
more negative the transmembrane voltage, i.e., more hyperpolarized, the higher was the magnesium influx rate
(Fig. 2). Conversely, depolarization of membrane voltage
diminishes Mg2⫹ uptake (70). The dependence of magnesium entry on the driving force induced by the electrochemical gradient indicates that Mg2⫹ entry may be mediated by an ion channel.
C. Schematic Model of Distal Cellular
Mg2ⴙ Transport
With the above information, we are able to speculate
on the mechanisms involved in magnesium absorption
within the DCT cell (Fig. 3). Because the transepithelial
2⫹
FIG. 2. Membrane voltage influences Mg
uptake in MDCT cells.
Mg2⫹ uptake was measured with microfluorescence according to the
methods given in the legend to Fig. 1. Transmembrane voltage was
measured with a voltage-sensitive fluorescent dye. Hyperpolarization
was achieved with addition of various concentrations of the membranepermeable anion SCN⫺ and depolarization with addition of various
concentrations of K⫹ to the bathing solution. The rate of Mg2⫹ influx,
d([Mg2⫹]i)/dt, was calculated in the first 500 s of the Mg2⫹ refill in the
presence of 1.5 mM MgCl2. Values are means ⫾ SE for 3– 6 cells. [Data
from Dai et al. (76).]
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
Peptide hormones
Parathyroid hormone
Calcitonin
Glucagon
Arginine vasopressin
␤-Adrenergic agonists
(isoproterenol)
Prostaglandins (PGE2)
Insulin
Mineralocorticoids (aldosterone)
Vitamin D [1,25(OH)2D3]
Magnesium restriction
Metabolic acidosis
Metabolic alkalosis
Hypermagnesemia
Hypercalcemia
Phosphate depletion
Potassium depletion
Diuretics
Furosemide
Amiloride
Chlorothiazide
MDCT Cells
Volume 81
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
(82). If an energy-dependent Mg2⫹ transporter were to
exist, it would appear that Mg2⫹ would act as a cofactor,
an energy source Mg2⫹-ATP2⫺, and a substrate (250).
Finally, it is unlikely that intracellular Mg2⫹ concentration
would normally fall to levels that would compromise
ATPase activity or Mg2⫹-ATP2⫺ levels (182, 183). Because
there is no evidence for an enzyme-dependent magnesium
pump at the present time, we have elected not to include
it in Figure 3. In this schematic view, the factors that
influence transcellular magnesium absorption include alterations of Mg2⫹ entry across the luminal membrane and
changes in Mg2⫹ exit across the basolateral membrane;
both of these steps may be modulated by the transmembrane voltage and concentration gradients across the respective membrane.
The properties of Mg2⫹ transport in the DCT, to some
extent, resemble those described for calcium handling.
Brunette et al. (46, 47) have described calcium uptake by
rabbit distal apical membrane vesicles through nifedipine-
sensitive Ca2⫹ channels. Matsunga et al. (206) further
claimed that these dihydropyridine-sensitive Ca2⫹ channels are activated by hyperpolarizing voltages. More recently, Hoenderop and co-workers (149, 150) have identified the gene coding the Ca2⫹ channel from rabbit CCD
and DCT that is activated by hyperpolarizing voltages and
inhibited by dihydropyridines (149, 150). These findings
concerning Ca2⫹ entry are in keeping with the earlier
ideas of Costanzo (63). On the other side of the cell, two
calcium transporters are responsible for Ca2⫹ efflux: an
ATP-dependent calcium pump and, at least in the distal
tubule, a Na⫹/Ca2⫹ exchanger (192, 264, 330). These properties of cellular Ca2⫹ handling are similar to those postulated here for Mg2⫹ transport, although the presence of
a Mg2⫹ pump and Na⫹/Mg2⫹ exchanger remains to be
determined. The regulation of distal magnesium reabsorption may share many of the controls identified for calcium
conservation but, as reviewed below, Mg2⫹ transport may
be specifically altered by influences not shared with calcium, thus affecting magnesium homeostasis independent
of calcium balance.
IV. LOAD DEPENDENCE OF MAGNESIUM
ABSORPTION IN THE DISTAL TUBULE
Distal magnesium absorption is load dependent in
that an increase in magnesium delivery to the DCT is
associated with an increase in magnesium absorption (19,
71, 248, 254). In one set of studies, rat distal tubules were
perfused with solutions containing variable magnesium
concentrations, and early and late collections were performed on the same distal tubule. These collection sites
were localized in the first 10 – 60% of the superficial distal
tubule and likely represent DCT rather than connecting
tubules or initial collecting ducts (254). The first studies
involved perfusing DCT with solutions containing zero
magnesium. No magnesium was detected in early or late
collections when the nephrons were perfused with magnesium-free Ringer solutions in either normal animals or
hypermagnesemic rats in which plasma magnesium was
elevated to increase the concentration gradient from
plasma to lumen. These data suggested that magnesium
absorption in the distal nephron is unidirectional, i.e.,
there is no magnesium secretion in the DCT. Net magnesium absorption was observed when the distal tubules
were perfused with solutions containing magnesium. Absolute magnesium absorption increased from 1.35 ⫾ 0.35
to 6.5 ⫾ 0.9 pmol䡠min⫺1䡠mm⫺1 as magnesium in the perfusate was increased from 0.5 to 2.5 mM; accordingly,
there was about a fivefold increase in magnesium absorption with about a fivefold increase in luminal magnesium
concentration (Fig. 4). PTH increased absolute and fractional magnesium absorption independent of delivery. Increased magnesium delivery due to hypermagnesemia or
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
FIG. 3. Schematic model of magnesium absorption in the distal
convoluted tubule. Conductive pathways and carrier-mediated transport
are denoted by solid arrows. Peptide hormones such as parathyroid
hormone (PTH), calcitonin, glucagon, and arginine vasopressin (AVP)
enhance magnesium reabsorption in the distal convoluted tubule (DCT).
The cellular mechanisms of these hormones are unknown but appear to
involve, in part, stimulation of cAMP release and activation of protein
kinase A, phospholipase C, and protein kinase C. The extracellular
Ca2⫹/Mg2⫹-sensing receptor modulates hormone-stimulated Mg2⫹ transport through G␣i protein coupling (20). Steroid hormones increase Mg2⫹
entry by transcriptional/translational mechanisms. Aldosterone increases hormone receptor-mediated Mg2⫹ entry, as indicated by the
broken arrows, and vitamin D metabolites by distinct pathways as yet
unknown (77; G. Ritchie, L.-j. Dai, D. Kerstan, H. S. Kang, L. Canaff, G. N.
Hendy, and G. A. Quamme, unpublished observations). Ca2⫹/Mg2⫹ sensing inhibits aldosterone- and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]mediated transcriptional gene expression. The sites of the transport
inhibitors such as dihydropyridines, thiazides, and amiloride are indicated (70, 76). [Modified from Quamme (251).]
55
56
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
hypercalcemia resulted in an increase in absolute absorption but a decrease in fractional transport (246, 254).
Other studies were performed where furosemide was
used to inhibit loop magnesium absorption, thereby increasing magnesium delivery to the DCT (248). Absolute
magnesium reabsorption increased from 0.6 ⫾ 0.2 to 3.0
⫾ 1.7 pmol䡠min⫺1䡠mm⫺1 with increased delivery, whereas
fractional absorption remained unchanged in these experiments. The basis for the dependence of magnesium absorption on magnesium delivery and luminal magnesium
concentration is also observed at the single-cell level (76).
Magnesium reabsorption in the DCT is under the control
of a number of hormones and altered by a number of
influences. However, the dependence of magnesium absorption with magnesium delivery is maintained in the
presence of these factors (246, 254).
V. HORMONAL CONTROL OF MAGNESIUM
TRANSPORT IN THE DISTAL
CONVOLUTED TUBULE
A. Peptide Hormones
1. PTH
A large number of hormones stimulate magnesium
absorption within the distal tubule (Table 1). The first to
be described was PTH. Infusion of PTH to thyroparathyroidectomized (TPTXed) animals increased the reabsorp-
tion of magnesium and diminished urinary magnesium
excretion (204). Micropuncture studies showed that part
of this hormonal action occurred within the distal tubule
(19, 131, 254). An increase in magnesium conservation
was observed even in the face of enhanced magnesium
delivery to this segment (248, 252, 254). The largest
changes were observed in TPTXed hamsters where the
mean tubular fluid-to-ultrafiltrable magnesium ratio
(TF/UFMg) at the distal sampling site fell from 0.56 ⫾ 0.08
to 0.33 ⫾ 0.08 after administration of PTH (131). This was
associated with a fall in fractional magnesium excretion
from ⬃14 to 3%. De Rouffignac et al. (287) and Bailly and
Amiel (16) have shown that PTH and other hormones
stimulate magnesium absorption in the rat distal tubule.
They used Brattleboro rats with hereditary diabetes insipidus, which lack endogenous ADH, and they infused either glucose or somatostatin to inhibit glucagon secretion. Furthermore, they TPTXed the animals to eliminate
circulating PTH and calcitonin. Thus a “hormone-deprived” animal model was created to serve as a basis for
evaluating the respective actions of each hormone (287).
Micropuncture studies were then performed to determine
the effects of hormone administration; importantly, these
studies were all performed with physiological hormone
concentrations. Infusion of PTH-(1O34) to hormone-deprived rats led to diminished magnesium and calcium
delivery to early and late distal tubule sampling sites (Fig.
5). These studies clearly demonstrate that PTH enhances
magnesium absorption within the distal tubule. Dai and
Quamme (75) showed that PTH also stimulates Mg2⫹
entry in isolated MDCT cells in excess of 30% above
control uptake rates. The change in transport was associated with increases in hormone-mediated cAMP formation, suggesting that PTH acts, in part, through protein
kinase A signaling pathways (Fig. 6).
2. Calcitonin
Calcitonin infusions have clearly been shown to enhance renal magnesium conservation in the rat (243).
Poujeol et al. (243) infused calcitonin to TPTXed rats and
observed a fall in fractional magnesium excretion from
4.1 ⫾ 0.4 to 1.0 ⫾ 0.3%, which they attributed to an
increase in magnesium reabsorption in the loop of Henle.
However, subsequent studies with the hormone-deprived
rat showed that calcitonin markedly stimulated fractional
magnesium absorption in the superficial distal tubule as
well as the loop (81). Fractional absorption in the distal
tubule increased by 27 ⫾ 6% in this study (Fig. 5). These
micropuncture studies indicate that calcitonin enhances
magnesium conservation, in part, by actions within the
distal tubule. Calcitonin has been shown to stimulate
intracellular cAMP formation and Mg2⫹ entry in MDCT
cells, indicating that the DCT segment of the distal tubule
is a target for this hormone (Fig. 6). Maximal concentra-
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
FIG. 4. Effect of luminal magnesium on net magnesium absorption
in the superficial rat distal tubule. Distal tubules were perfused from the
proximal tubule at constant flow rates (25 nl/min) with solutions containing variable MgCl2 concentrations (0 – 4 mM). Magnesium absorption
was calculated by comparing the delivery rates at early and late collection sites along the same perfused distal tubule. Magnesium was quantitated by electron microprobe analysis and water absorption with the
use of inulin. The results are from thyroparathyroidectomized rats. [Data
from Quamme and Dirks (254).]
Volume 81
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
57
lar cAMP generation, and inhibited by the channel blocker
nifedipine. Clearly, of the segments comprising the distal
tubule, the evidence from this study indicates that the
convoluted portion is involved with glucagon-induced
magnesium conservation.
4. Arginine vasopressin
tions of calcitonin increased Mg2⫹ uptake by 49 ⫾ 5%,
which is greater than that observed for PTH. Again, hormone-stimulated Mg2⫹ entry rates were associated with
increases in intracellular cAMP levels.
3. Glucagon
Glucagon is a potent renal magnesium-conserving
hormone (16). Bailly and Amiel (16) reported that the
acute infusion of pharmacological concentrations of glucagon in parathyroid gland-intact rats leads to a rapid fall
in fractional magnesium excretion from 16 ⫾ 1 to 9 ⫾ 2%
(16). The response to glucagon is even greater in hormone-deprived animals. Bailly et al. (19) showed that
fractional magnesium excretion markedly decreased by
⬃50% (from 71.5 ⫾ 8.0 to 39.6 ⫾ 5.7 nmol/min) with
glucagon administration in rats deficient in endogenous
PTH, calcitonin, glucagon, and antidiuretic hormone. This
was attributed to a doubling of absolute reabsorption
within both the loop of Henle (increase from 6.5 ⫾ 0.7 to
11.7 ⫾ 0.7 nmol/min) and the distal tubule (increase from
0.85 ⫾ 0.1 to 1.75 ⫾ 0.3 nmol/min). Accordingly, glucagon
acts within the loop and distal tubule of the rat.
We have performed studies in isolated MDCT cells to
determine the cellular mechanisms of hormonal stimulation of magnesium transport (67). Glucagon maximally
increased Mg2⫹ uptake by ⬃20% (Fig. 6). This stimulation
was concentration dependent, associated with intracellu-
FIG. 6. Peptide hormones stimulate intracellular cAMP formation
and Mg2⫹ uptake in Mg2⫹-depleted mouse distal convoluted tubule
(MDCT) cells. Confluent MDCT cells were cultured in Mg2⫹-free media
(⬍0.01 mM) for 16 –20 h. Measurement of cAMP was performed with
radioimmunoassay. Fluorescence studies were performed in buffer solutions in the absence of Mg2⫹, and where indicated, MgCl2 (1.5 mM final
concentration) was added to observe changes in intracellular Mg2⫹
concentration. PTH, calcitonin, glucagon, and AVP were added to the
buffer solution where indicated. Values are means ⫾ SE. *Changes in
significance (P ⬍ 0.01) of Mg2⫹ uptake. and ⫹Significance (P ⬍ 0.001) of
cAMP release from the respective control values. [Data from Dai et al.
(67, 69) and G. Ritchie, L.-j. Dai, D. Kerstan, H. S. Kang, L. Canaff, G. N.
Hendy, and G. A. Quamme, unpublished data.]
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
FIG. 5. Fractional reabsorption of magnesium in the superficial
distal tubule. Studies were performed in “hormone-deprived” rats lacking vasopressin, PTH, calcitonin, and glucagon. Tubular fluid was collected from the early and late sites of the same distal tubule, and net
magnesium reabsorption is expressed as a fraction of that delivered to
the segment. The PTH (5 mU/min) and glucagon (5 ng/min) studies were
from Bailly et al. (19), and those of calcitonin (1.0 mU/min) and AVP (20
pg/min) were from Elalouf et al. (92) and Rouffignac et al. (286), respectively. Values are means ⫾ SE. *Significance from the respective control
values.
The actions of arginine vasopressin (AVP) within the
DCT are poorly understood (165). AVP has been shown to
be an effective magnesium-conserving hormone in anesthetized and conscious hormone-deprived rats (37, 93,
286). Micropuncture studies of these animals have shown
that AVP actions occur principally within Henle’s loop
(93). Elalouf et al. (93) failed to discern any change in
fractional magnesium absorption in the superficial distal
tubule after physiological administration of AVP (93). In
these studies, Elalouf et al. (93) reported that fractional
calcium absorption significantly increased from 42.0 ⫾ 5.8
to 62.8 ⫾ 7.1%, whereas the change in fractional magnesium transport with AVP was not significant although it
increased from 45.5 ⫾ 7.8 to 55.3 ⫾ 15.5% (Fig. 5). These
changes may have been significant if a greater number of
tubules were sampled. Costanzo and Windhager (65) did
not observe any change in calcium absorption in the
microperfused rat distal tubule with administration of
AVP. These animals were TPTXed but not hormone deprived as were those used by Elalouf et al. (93). In both
studies, AVP enhanced sodium absorption in the distal
tubule.
58
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
5. Cellular mechanisms of peptide hormone actions
The cellular mechanisms underlying the hormonal
actions on distal magnesium absorption are becoming
clearer. Morel and co-workers (17, 215) have shown that
PTH, calcitonin, and glucagon stimulate receptor-mediated cAMP release in the DCT (45). They also reported
that AVP receptors may be present in the DCT, but there
were marked species differences in adenylate cyclase
responsiveness (217). There was little AVP-stimulated
cAMP release in the DCT of the rabbit and human, intermediate response in the mouse, and greatest in the rat
(215). We have shown that PTH, calcitonin, glucagon, and
AVP stimulate Mg2⫹ uptake into MDCT cells (21, 67, 69;
Fig. 6). Friedman and Gesek (108, 113, 117) reported that
these hormones also stimulate cellular cAMP accumulation. We have demonstrated that an increase in exogenous intracellular cAMP, with 8-bromo-cAMP, or endogenous cAMP formation, with forskolin, increased Mg2⫹
uptake, whereas inhibition of protein kinase A with RpcAMPS prevented hormone-stimulated uptake (67). Accordingly, receptor-mediated cAMP release and activation
of protein kinase A plays a role in hormone-stimulated
Mg2⫹ uptake in MDCT cells. However, it is apparent that
other signaling pathways are present for hormone-mediated Mg2⫹ uptake in MDCT cells. Hormone-stimulated
Mg2⫹ uptake rates do not correlate with the measured
intracellular cAMP levels in MDCT cells (38, 107, 138).
Furthermore, phospholipase C inhibition with U-73122
and protein kinase C inhibition with Ro31– 8220 abolished
PTH- and calcitonin-stimulated Mg2⫹ uptake (Fig. 7). This
was true for all of the hormones tested: PTH, calcitonin,
glucagon, and AVP (67– 69; L.-j. Dai, G. Ritchie, D. Kerstan, H. S. Kang, and G. A. Quamme, unpublished observations). We have previously reported that chelerythrine,
a putative protein kinase C inhibitor, did not alter hor-
2⫹
FIG. 7. PTH stimulates Mg
uptake through cAMP- and phospholipase C-mediated pathways. The inhibitors for protein kinase A, RpcAMPS, phospholipase C, U-73122, protein kinase C, and Ro31– 822,
were added at concentrations of 0.05, 15, and 0.1 ␮M, respectively, 10
min before the determination of Mg2⫹ uptake with and without PTH
(10⫺7 M). Values are means ⫾ SE. *Significance (P ⬍ 0.01) of Mg2⫹
uptake in the presence of Rp-cAMPS versus control for PTH, respectively. ⫹Significance (P ⬍ 0.01) of cAMP and Mg2⫹ entry rates with PTH
vs. the respective control values. [Data from Dai et al. (74) and G.
Ritchie, L.-j. Dai, D. Kerstan, H. S. Kang, L. Canaff, G. N. Hendy, and G. A.
Quamme, unpublished data.]
mone-mediated responses (67, 69). However, this agent
has recently been shown to have no inhibitory actions on
protein kinase C (176). Our evidence indicates that protein kinase C is involved in hormone signaling responses
in MDCT cells; however, the isotype(s) of protein kinase
C is not known. These hormones do not elicit receptormediated intracellular Ca2⫹ transients, suggesting that
Ca2⫹ signaling is not involved with the responses (110,
116). It is well known that multiple receptors can converge on a single G protein, and in many cases a single
receptor can activate more than one G protein and
thereby modulate multiple intracellular signals (128). It is
evident that cAMP-dependent protein kinase A, phospholipase C, and protein kinase C pathways are necessary for
hormone-stimulated Mg2⫹ entry into MDCT cells. The
details of how peptide hormones act on Mg2⫹ transport in
MDCT cells and intact distal tubules are unknown.
These observations of hormone-stimulated Mg2⫹ entry are somewhat different from those reported for Ca2⫹
entry into MDCT cells. Friedman and Gesek (108, 113,
117) showed that PTH and calcitonin increased calcium
uptake in the DCT through changes in membrane voltage.
They provided evidence that receptor-mediated increases
in cAMP activate basolateral Cl⫺ channels resulting in
cellular efflux of Cl⫺, diminished intracellular Cl⫺ activity, and hyperpolarization of the apical membrane of the
MDCT cell through a decrease in the electrochemical Cl⫺
gradient (110). Membrane hyperpolarization activates
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
AVP also stimulates Mg2⫹ entry into MDCT cells in a
concentration-dependent fashion that is sensitive to nifedipine (Fig. 6). These observations suggest that AVP
plays a role in control of magnesium conservation within
the DCT (67). Many of the hormones that have been
shown to increase magnesium reabsorption in the distal
tubule have additive effects (91, 285). AVP and glucagon
are additive, below maximal concentrations, in stimulating Mg2⫹ uptake into MDCT cells (67). Accordingly, these
hormones, and probably others, together orchestrate
magnesium reabsorption in the distal tubule. It would be
difficult to predict the effects of one hormone on a background of many. This was the rationale for De Rouffignac
(285) using hormone-deprived animals in their studies
investigating individual hormone effects. The advantage
of using isolated MDCT cells is that hormone-mediated
signaling pathways may be investigated, which is difficult
or impossible to perform with in vivo studies.
Volume 81
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
mone signaling within the two segments is qualitatively
different. The differential control of calcium reabsorption
within the DCT and CCD and magnesium transport in the
DCT provides a unique mechanism to differentially regulate renal calcium and magnesium balance.
B. Steroid Hormones
1. Mineralocorticoid hormones
Mineralocorticoid receptors are present in DCT cells,
which are thought to be involved in expression of NaCl
cotransport, Na⫹ conductance, and sodium pump activity
(57, 283, 333). The effects of aldosterone on distal tubule
magnesium absorption have not been studied with micropuncture techniques. Clearance studies have shown
that chronic aldosterone administration results in renal
magnesium wasting, but this has been explained by extracellular volume expansion leading to diminished NaCl
and magnesium reabsorption within the loop (202, 203,
319). We have studied the effects of aldosterone on Mg2⫹
entry into MDCT cells (77). Incubation of aldosterone, for
16 h before determination of Mg2⫹ uptake, failed to have
any effect on basal magnesium transport. However, pretreatment of MDCT cells with aldosterone potentiated
hormone-stimulated Mg2⫹ uptake (Fig. 8). This was associated with potentiation of hormone-mediated cAMP release in aldosterone-treated MDCT cells (77). Cycloheximide, an inhibitor of protein synthesis, abolished the
potentiation of aldosterone on hormone-stimulated cAMP
release and Mg2⫹ uptake (59). Accordingly, aldosterone
FIG. 8. Aldosterone potentiates hormone-stimulated intracellular
cAMP formation and Mg2⫹ entry in MDCT cells. MDCT cells were
treated with aldosterone (10⫺7 M) where indicated for 16 h before cAMP
determinations and fluorescent measurements. PTH (10⫺7) was added 5
min before cAMP and immediately with Mg2⫹ uptake determinations.
Values are means ⫾ SE. *Significance (P ⬍ 0.01) of Mg2⫹ uptake values.
⫹
Significance (P ⬍ 0.001) of cAMP analysis from control values. [Data
from Dai et al. (77).]
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
Ca2⫹ entry and increases the driving force for Ca2⫹ movement into the cell which, in turn, is removed across the
basolateral membrane into the blood. More recent studies
indicate that PTH-mediated stimulation of calcium transport is through intermediary pathways involving activation of both protein kinase A and protein kinase C (107,
144). PTH and other hormones may also directly act on
Ca2⫹ entry through apical Ca2⫹ channels and Ca2⫹ exit
through Na⫹/Ca2⫹ exchange, again through activation of
these kinases (10, 11, 38). Brunette and co-workers (144,
174) have shown that distal luminal vesicles prepared
from rabbit tubules pretreated with PTH transport much
more calcium than vesicles from untreated tubules, inferring a covalent modification of putative apical Ca2⫹ channels. Accordingly, PTH and possibly other hormones may
have direct actions on Ca2⫹ entry in addition to their
ability to alter the membrane voltage. Further research is
required to determine the cellular mechanisms underlying
the action of these hormones on distal divalent cation
absorption. Interestingly, Friedman and Gesek (108)
failed to demonstrate any effect of glucagon and AVP on
Ca2⫹ entry into MDCT cells, although these hormones
increased cellular cAMP accumulation (108). It is apparent that hormonal controls of Ca2⫹ entry in MDCT cells
are different from those reported for Mg2⫹. In support of
this notion, differential controls of renal Ca2⫹ and Mg2⫹
transport are apparent in the clinical presentation of
many familial and acquired diseases (see sects. IX and X).
Finally, a comment should be made concerning the
differences between hormone-mediated Ca2⫹ within the
CCD and hormone-stimulated Mg2⫹ uptake in MDCT cells
because it emphasizes different controls for these two
divalent cations in the distal tubule. Hoenderop et al.
(151) have extensively characterized hormone-stimulated
Ca2⫹ transport in primary rabbit CCD cells. The rabbit
CCD does not reabsorb Mg2⫹ even with chronic magnesium depletion (R. J. M. Bindels, personal communication). However, the comparisons of hormonal controls
between the two segments are informative. The rate of
transepithelial Ca2⫹ reabsorption within the rabbit CCD is
determined by an apical 1,25-dihydroxyvitamin D3
[1,25(OH)2D3]-responsive calcium channel (149). This
Ca2⫹ channel (ECaC) is activated by hyperpolarization
but does not transport Mg2⫹, nor does external Mg2⫹
inhibit Ca2⫹ transport, clearly different from the Mg2⫹
transporter (150). Ca2⫹ reabsorption is stimulated by peptide hormones such as PTH and AVP (32). It has been
reported that Ca2⫹ transport is stimulated by hormonemediated signaling pathways that are independent of
cAMP but involve a chelerythrine-inhibitable protein kinase C that is not downregulated after chronic phorbol
ester treatment (31, 146, 155, 331). Our studies have
shown that both cAMP-protein kinase A and protein kinase C (not sensitive to chelerythrine) are essential in
hormonal action within the MDCT cells. Accordingly, hor-
59
60
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
2. Vitamin D3 metabolites
Vitamin D3 metabolites have important effects on
mineral metabolism by 1,25(OH)2D3 actions on epithelial
transport. Although it is clear that 1,25(OH)2D3 increases
calcium and magnesium absorption within the intestine,
its actions within the kidney are unclear (172, 332). The
1,25(OH)2D3-dependent calcium binding proteins, calbindin-D9K and calbindin-D28K, have long been thought to be
involved in facilitating calcium transport across epithelial
cells (100, 172, 332). The mechanisms of calcium stimulation are obscure, but because of its close association
with the basolateral membrane, it is postulated that they
somehow increase the calcium pump (Ca2⫹-Mg2⫹-ATPase) activity (33, 36, 172). Within the kidney, calbindin-D
is localized in the distal tubule where a significant portion
of calcium and magnesium is reabsorbed (187, 197, 284,
316, 324) . The distal tubule, including the convoluted
segment, also possesses 1,25(OH)2D3 receptors (186, 187,
284). Accordingly, 1,25(OH)2D3 and perhaps its dependent calbindin-D may have significant actions within the
DCT. The effects of 1,25(OH)2D3 and calbindins on magnesium transport are unknown. Calbindin-D9K has a relatively high affinity for Mg2⫹ (6, 49, 185), and it is appropriately altered by changes in magnesium balance (137),
suggesting a role for these binding proteins in renal magnesium control.
In contrast to calcium, little information is available
concerning the effects of vitamin D3 metabolites on tubular Mg2⫹ transport. On balance, data from clinical or
experimental studies indicate little or no effect of
1,25(OH)2D3 on renal magnesium handling as determined
by clearance techniques (51, 129, 130, 184, 213, 219, 270).
There have been no micropuncture studies performed to
localize the actions, if any, of vitamin D3 on magnesium
transport. The effects of 1,25(OH)2D3 on renal calcium
absorption are more substantial but not clear (32, 39, 40,
64, 166). The most convincing data demonstrating that
1,25(OH)2D3 may have some direct effects on Ca2⫹ transport are those using isolated cells. Bindels and co-workers (32, 330) showed that 1,25(OH)2D3 increased calbindin-D28k and stimulated transcellular calcium absorption
in primary cultures of the rabbit CCD. The maximal response occurred about 48 h posttreatment, suggesting to
these investigators that the response involved initiation of
transcriptional processes (32). The responses of
1,25(OH)2D3 were independent of PTH and not additive to
PTH-stimulated Ca2⫹ transport. In a more recent report,
these authors have shown that 1,25(OH)2D3 increased
calbindin-D28k RNA and protein content without a change
in Na⫹/Ca2⫹ exchanger or Ca2⫹-ATPase RNA and protein
(32). The second study to clearly show effects of vitamin
D3 metabolites on calcium transport was performed in
MDCT cells by Friedman and Gesek (109). These workers
reported that 1,25(OH)2D3 did not alter basal Ca2⫹ uptake
but accelerated PTH-dependent calcium entry rates. This
response was rapid, concentration dependent, significant
at 2 h and maximal by 5 h, and mediated by transcriptional processes because it was inhibited by cycloheximide (109). The reasons for the discrepancies between
these two reports are not known; it may be the cell type
used in the two separate studies or the techniques by
which calcium transport was measured. Nevertheless, it is
clear that 1,25(OH)2D3 increases calcium-binding protein
in distal tubules and suggests that it may have significant
actions on basal or hormone-mediated calcium transport.
Lui et al. (186) have shown that 1,25(OH)2D3 enhances calbindin-D in murine distal cells as it does
in other species (8, 59, 66, 330). Friedman and Gesek
(110) have reported that the MDCT cell line used here
possesses calbindin-D. We have demonstrated that
1,25(OH)2D3 increases Mg2⫹ entry rates in MDCT cells
(Fig. 9). The response is concentration dependent, involves transcriptional processes involving de novo protein synthesis, and does not appear to be related to
cAMP-mediated stimulation of Mg2⫹ uptake (G. Ritchie,
L.-j. Dai, D. Kestan, H. S. Kang, L. Canaff, G. N. Hendy,
and G. A. Quamme, unpublished observations). Finally,
1,25(OH)2D3-stimulated Mg2⫹ transport is additive to
PTH-mediated uptake, suggesting that the peptide and
steroid hormones regulate magnesium absorption
through distinctive intracellular signaling pathways (Fig.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
may enhance hormone-stimulated Mg2⫹ entry by increasing cAMP and its responses. This notion is supported by
the observations of others (155). Rajerison et al. (259)
demonstrated that adrenalectomy reduced AVP-stimulated adenylate cyclase activity in membrane fractions
prepared from rat kidney medulla. Doucet and co-workers (85, 95) have shown that glucagon- and AVP-responsive cAMP generation is diminished in thick ascending
limb and collecting tubule segments harvested from adrenalectomized rats compared with animals treated with
physiological doses of aldosterone. These investigators
postulate that aldosterone induces a protein(s) that stimulates hormone-sensitive adenylate cyclase activity. Studies with kidney membrane fractions and isolated segments in the absence of aldosterone demonstrated an
impairment of coupling between hormone receptors and
adenylate cyclase catalytic units that was responsible for
diminished cAMP generation (95). Steroid hormones have
significant effects on expression and posttranslational targeting of heterotrimeric G proteins so that associated
channels are covalently modified (218, 281, 293). The
mechanism(s) through which steroids control G␣S proteins (synthesis and/or degradation vs. activity of each
unit) associated with Mg2⫹ uptake in MDCT cells is not
known (85). The role of mineralocorticoids in the physiological maintenance of renal magnesium handling also
requires further research.
Volume 81
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
9). These studies show that vitamin D3 metabolites modulate magnesium transport in the DCT.
Vitamin D3 administration has often been associated
with increases in urinary magnesium and calcium excretion. Vitamin D3 metabolites increase intestinal absorption of magnesium and calcium so that a positive divalent
cation balance may lead to hypermagnesemia and hypercalcemia and increased divalent cation urinary excretion
over time. Vitamin D3 induces hypermagnesemia and hypercalcemia that diminishes magnesium absorption in the
loop of Henle (254) and distal tubule (20, 254) through the
extracellular Ca2⫹/Mg2⫹-sensing receptor (see sect. VI).
This may also explain the increase or no change in urinary
magnesium excretion after administration of vitamin D3.
The net effect on magnesium balance would thus depend
on the relative magnitudes of vitamin D3 actions at the
intestinal and renal levels.
C. Prostaglandins
PGE2 is the major arachidonate metabolite synthesized by cyclooxygenase in the mammalian kidney. PGE2
has a number of diverse actions on the kidney in addition
to its ability to influence renal hemodynamics. PGE2 inhibits NaCl absorption within the thick ascending limb
(313) and modulates sodium and water transport in the
CCD (134, 135). On balance, prostaglandins are thought to
be natriuretic by way of their actions on the thick ascending limb and CCD (18, 313). Three clearance studies con-
cluded that arachidonic acid metabolites inhibit tubular
reabsorption of calcium and magnesium resulting in increased urinary excretion (106, 282, 295). Schneider et al.
(295) infused PGE2 into dog renal arteries and showed
that calcium and magnesium excretion increased in association with a rise in urinary sodium excretion. Roman et
al. (282) and Friedlander and Amiel (106) reported that
meclofenamate or indomethacin infusion in rats decreased fractional magnesium excretion by ⬃40%. Again,
the changes in urinary magnesium and calcium were associated with similar changes in sodium excretion. Because
PGE2 inhibits NaCl absorption in the thick ascending limb, it
may be expected that prostaglandins would increase calcium and magnesium excretion through diminished reabsorption in the loop (342). However, van Baal et al. (330)
have shown that PGE2 stimulated calcium reabsorption in
the rabbit CCD segment of the distal tubule. They reported
that PGE2 stimulated net apical-to-basolateral calcium transport in CCD cells grown to confluence on permeable supports. PGE2 also stimulated cAMP formation in these cells,
initially suggesting that protein kinase A-dependent pathways were involved (249). However, in a later preliminary
report, these investigators reported that the changes in
PGE2-stimulated calcium transport were not directly associated with cAMP formation so that other signaling pathways may be present in rabbit CCD cells (146). Finally, van
Baal et al. (329) have shown that primary CCD cells produce
endogenous prostaglandins that affect basal calcium transport. Like the CCD, the DCT synthesizes prostaglandins,
principally PGE2 (35, 99). The above functions are mediated
by four different prostaglandin receptors (EP1, EP2, EP3, and
EP4) that are selectively located to the apical and/or basolateral epithelial membranes (42, 61, 135, 291, 317, 329). EP1
and EP3 subtypes mediate intracellular Ca2⫹ signaling and
inhibition of adenylate cyclase, respectively, that result in
inhibition of NaCl absorption within the thick ascending
limb (313) and CCD (107, 155, 244) and AVP-stimulated
water transport in the CCD (134). EP2 and EP4 subtypes are
coupled to adenylate cyclase that upon stimulation enhances transepithelial calcium transport in the rabbit CCD
(329). Moreover, these receptors may be colocalized to the
same cell type but polarized to apical or basolateral membranes (135, 213, 329). Van Baal et al. (329) have shown that
apical and basolateral PGE2 stimulate calcium absorption
through EP2 and/or EP4 receptors, whereas activation of
basolateral EP3 receptors inhibits basal and hormone-stimulated calcium transport. We have shown that PGE2 is a
potent stimulator of Mg2⫹ uptake into MDCT cells (69).
These actions are, in part, through cAMP-mediated mechanisms, but we were unable to determine the polarization of
receptors because the immortalized MDCT cells used do not
form tight junctions and are unlikely to be polarized (110).
Accordingly, it is not known if the PGE2 effects in the DCT
are due to luminal or basolateral prostaglandin. We infer
from these results with MDCT cells that prostaglandins may
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
2⫹
FIG. 9. 1,25(OH)2D3 and PTH stimulate Mg
entry into MDCT cells
by separate mechanisms. Maximally effective concentrations of
1,25(OH)2D3 (10⫺7 M) and PTH (10⫺7 M) were added where indicated.
cAMP was measured by radioimmunoassay and d([Mg2⫹]i)/dt by fluorescence. Values are means ⫾ SE for 4 or 5 preparations. *Significance
(P ⬍ 0.01) of Mg2⫹ uptake rates. ⫹Significance of cAMP concentrations
following PTH or 1,25(OH)2D3 plus PTH compared with the respective
control values. 䊐Significance (P ⬍ 0.01) of Mg2⫹ uptake of 1,25(OH)2D3
vs. 1,25(OH)2D3 plus PTH. [Data from Dai et al. (68).]
61
62
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
Volume 81
modulate distal tubule magnesium transport and together
with peptide and steroid hormones orchestrate renal magnesium conservation.
D. Insulin
2⫹
FIG. 10. Insulin potentiates PTH-stimulated Mg
entry into MDCT
cells. Maximal concentrations of insulin (10⫺7 M) and PTH (10⫺7 M)
were added where indicated. cAMP was measured by radioimmunoassay and d([Mg2⫹]i)/dt by fluorescence. Values are means ⫾ SE for 3–5
preparations. * and ⫹Significance (P ⬍ 0.01) of Mg2⫹ entry rates and
cAMP concentrations, respectively, compared with the respective control values. 䊐Significance (P ⬍ 0.01) of these data for insulin plus PTH
compared with either insulin or PTH alone. [Data from Dai et al. (68).]
sponses are complicated because aldosterone had no
effect on insulin actions but potentiated PTH-stimulated cAMP and Mg2⫹ uptake (77). Although the intracellular mechanisms are unclear, we infer from these
studies that insulin plays a singular role in control of
magnesium conservation and modulates hormonal regulation of magnesium transport within the distal tubule.
E. Other Hormones and Factors
1. ␣- and ␤-adrenergic agonists
The nephron is richly innervated along its length
from the glomerulus to the collecting tubule (22). Renal
nerve stimulation significantly increases NaCl and water
reabsorption in the proximal tubule, loop of Henle, and
distal tubule (83, 113). Renal nerves also mediate calcium
reabsorption through ␣-adrenergic receptors (14). Gesek
(113) has reported that MDCT cells possess ␣2-adrenergic
receptors, and epinephrine or B-HT 933, an ␣2-agonist,
stimulates Na⫹ uptake and Na⫹-K⫹-ATPase activity in this
cell line. This response was dependent on protein kinase
C activity and was associated with increases in phospholipase C and inositol 1,4,5-trisphosphate and diacylglycerol, but ␣2-agonists had no effect on basal or hormonestimulated cAMP accumulation (113, 114). These findings
are consistent with a pertussis toxin-insensitive mechanism. Interestingly, Gesek (113) was unable to observe an
effect on Ca2⫹ uptake in MDCT cells. The actions of
␣-adrenergic agonists on Mg2⫹ transport in the DCT have
not been studied.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
Insulin has clearly been shown to have antinatriuretic and antimagnesiuric effects by its actions on the
thick ascending limb of the loop of Henle (78, 79, 153,
163, 195). Among the tubular segments studied, insulin
receptor binding is highest along the thick ascending
limb and DCT so that by inference insulin may affect
electrolyte transport within the DCT as well as the loop
(52, 101, 105, 221). Insulin also stimulates sodium transport in A6 cells, which are a distal cell line from Xenopus laevis that have properties similar to the mammalian distal nephron (143, 205, 262). Insulin-stimulated
sodium transport was partly inhibited by genistein, indicating tyrosine kinase was important but was independent on cAMP levels (262). Insulin did not increase
cAMP formation in A6 cells, nor did adenylate cyclase
inhibition diminish transport (205, 276). Because
genistein did not completely inhibit insulin actions,
Rodriguez-Commes et al. (276) suggested that parallel
non-tyrosine kinase-dependent pathways were also involved. They showed that insulin actions in A6 cells
required intracellular Ca2⫹ signaling, suggesting to
these investigators that protein kinase C is needed for
some of the responses. Clearly, the insulin-receptor
signaling pathways are different in the various cell
types studied. We have recently shown that insulin
stimulates Mg2⫹ uptake in MDCT cells (77). Insulin
stimulated Mg2⫹ entry in a concentration-dependent
manner with maximal response of 214 ⫾ 12 nM/s, which
represented a 30 ⫾ 5% increase in the mean uptake rate
above control values, d([Mg2⫹]i)/dt, of 164 ⫾ 5 nM/s.
This was associated with a 2.5-fold increase in insulinmediated cAMP generation, 52 ⫾ 3 pmol䡠mg protein⫺1䡠5
min⫺1. Genistein, a tyrosine kinase inhibitor, diminished insulin-stimulated Mg2⫹ uptake, back to control
values, 169 ⫾ 11 nM/s, but did not change insulinmediated cAMP formation, 47 ⫾ 5 pmol䡠mg protein⫺1䡠5
min⫺1. The evidence is that insulin stimulates Mg2⫹
entry into MDCT cells through genistein-sensitive tyrosine phosphorylation. Additionally, insulin stimulates
cAMP formation in MDCT cells and presumably activates protein kinase A (77). Maximal concentrations of
PTH plus insulin increased cAMP levels and Mg2⫹ entry
rates to a greater extent than each of the hormones
alone (Fig. 10). Mandon et al. (195) have explained this
potentiation of insulin with other peptide hormones as
interactions at different sites along the established hormone-adenylate cyclase signaling system. The actions
of insulin-mediated effects on peptides hormone re-
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
nesium absorption in both the loop and distal tubule. This
organization may be of benefit because influences acting
in either the loop or distal tubule may be modified by
changes in the other segment.
The interactions of the various peptide and steroid
hormones, prostaglandins, and renal innervations are
complex (251, 285). It can be inferred that overall distal
magnesium absorption is controlled by all of these influences initiated individually but coming together through
shared intracellular signaling pathways. Few studies have
been directed at describing these interactions. Clearly,
control of renal magnesium handling is important enough
to warrant multiple hormonal control.
VI. EXTRACELLULAR CALCIUM/MAGNESIUMSENSING RECEPTORS IN THE DISTAL
CONVOLUTED TUBULE
2. Other endocrine and paracrine factors
In addition to the hormones indicated above, others
may be involved in regulation of magnesium reabsorption
within the DCT including kinins and growth factors (239).
Hoenderop et al. (147) have reported that adenosine increases Ca2⫹ reabsorption in rabbit CNT and CCD cells.
Adenosine responses were through A1 receptor-mediated
pathways involving activation of phospholipase C. Stimulation of Ca2⫹ transport was independent of cAMP and
protein kinase C activity, suggesting that an additional
unidentified signaling pathway may be involved in adenosine responses. Based on these observations, we tested
whether adenosine stimulates Mg2⫹ uptake in MDCT
cells. Adenosine did not have any effect on Mg2⫹ increase
in MDCT cells but stimulated cAMP formation, indicating
the presence of A2 receptors acting through Gs coupling.
There was no evidence for A1 receptors in this cell line.
Additionally, DCT cells, including MDCT cells, have P2
purinogenic receptors that modulate distal hormone-sensitive calcium transport (167). Finally, ANP receptors are
present in the DCT and MDCT cells, but the effects on
magnesium transport have not been studied (Dai et al.,
unpublished observations). ANP stimulates calcium reabsorption in rabbit CCD through cGMP-dependent protein
kinase type III (148).
F. Hormonal Regulation and Renal Mg2ⴙ Handling
Micropuncture and microperfusion studies and experiments with isolated cells have shown that many hormones regulate magnesium absorption in the distal tubule. Interestingly, with the exception of prostaglandins,
all of these hormones and factors also increase magnesium transport in the thick ascending limb of the loop of
Henle (285). Accordingly, these hormone-mediated responses are serially organized to similarly regulate mag-
An extracellular Ca2⫹/Mg2⫹-sensing receptor has recently been shown to be expressed along the entire length
of the nephron, particularly the loop of Henle, DCT, and
inner medullary collecting duct (267, 268, 349). This receptor is very similar to the one expressed in the parathyroid gland (44, 45). It comprises three major domains:
1) a large extracellular amino-terminal domain consisting
of 613 amino acids, which is thought to possess cationic
binding sites; 2) a 250-amino acid domain with 7 predicted
membrane-spanning segments characteristic of the G protein-coupled receptor family; and 3) a carboxy-terminal
domain of 222 amino acids that likely resides in the
cytoplasm and is involved with intracellular signaling processes (44). The evidence is that elevated plasma Ca2⫹ or
Mg2⫹ binds to the extracellular domain of the receptor
and initiates a number of intracellular signals. Among
these is stimulation of G␣i proteins that modulate adenylate cyclase activity and cAMP levels and G␣q proteins that
activate phospholipase C releasing inositol 1,4,5-trisphosphate and cytosolic Ca2⫹ (44). Hebert and co-workers
(136, 292, 336) postulate that elevated plasma calcium or
magnesium and activation of the Ca2⫹/Mg2⫹-sensing receptor leads to diminished salt (sodium, calcium and
magnesium) transport within the loop and water absorption within the inner medullary collecting duct. This results in an increase in urinary water flow in addition to
calcium and magnesium excretion, minimizing the opportunity of stone formation. Riccardi et al. (266) and Yang et
al. (349) have shown that the Ca2⫹/Mg2⫹-sensing receptors are also present on the basolateral membrane of the
DCT. Ca2⫹/Mg2⫹-mediated intracellular signaling may
have important effects on distal cellular function including sodium, potassium, and divalent cation transport
(136, 228).
We have recently shown that MDCT cells possess a
Ca2⫹/Mg2⫹-sensing mechanism(s) that is equally sensitive
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
␤-Adrenergic agonists also mediate direct effects on
tubular transport (22, 211). Although ␤-adrenergic agents
have been shown to increase magnesium absorption in
the thick ascending limb, no experiments have been directed at the distal tubule (18). Gesek and White (119)
have demonstrated that MDCT cells possess ␤1- and ␤2receptor subtypes that upon activation with isoproterenol
elicited marked increases in cAMP formation (119). Recently, we tested the effects of ␤-adrenergic receptor
activities on Mg2⫹ uptake in Mg2⫹-depleted MDCT cells.
Isoproterenol increased Mg2⫹ entry by 18 ⫾ 4% and cAMP
formation 3.2-fold above control values. Although not
tested, ␤-adrenergic activation may stimulate Mg2⫹ uptake through cAMP-mediated pathways (119). We infer
from these studies with MDCT cells that renal nerves and
circulating catecholamines may play a role in control of
magnesium transport in the distal tubule.
63
64
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
to extracellular Ca2⫹ and Mg2⫹ concentrations normally
found in the plasma (21). Figure 11 summarizes the comparative effects of extracellular Mg2⫹ and Ca2⫹ on glucagon-mediated intracellular cAMP accumulation. The halfmaximal effective concentrations were 0.5 mM Mg2⫹ and
1.5 mM Ca2⫹, which are consistent with normal plasma
concentrations. This is unlike the observations with other
cells where extracellular Ca2⫹ has been found to be a
more potent stimulator of Ca2⫹/Mg2⫹-sensing receptorinduced intracellular signaling than external Mg2⫹. The
threshold value for extracellular Ca2⫹ has been reported
to be on the order of 1–5 mM for renal cells, whereas a
similar cytosolic Ca2⫹ response requires as much as 5–20
mM Mg2⫹ (241, 261). These relative potencies of extracellular Ca2⫹ and Mg2⫹ recapitulate their actions in bovine
parathyroid cells and in Xenopus oocytes injected with
cRNA and HEK 293 cells transfected with DNA of the
cloned Ca2⫹/Mg2⫹-sensing receptor (43, 55, 222). Thus it
was of interest that the polyvalent cation-sensitive mechanism of MDCT cells was apparently as sensitive to extracellular Mg2⫹ as it was to Ca2⫹. This is particularly
noteworthy because the Mg2⫹ studies were performed in
the presence of normal or elevated Ca2⫹ (21). The functional consequences of changes in the amino acid sequence of the Ca2⫹/Mg2⫹-sensing receptor have been investigated by expressing a variety of mutated receptors in
HEK 293 cells (13). Some of the mutations diminish Ca2⫹/
Mg2⫹-sensing receptor signaling, others enhance the sensitivity to external Ca2⫹, and still others are completely
nonfunctional with no intracellular signaling as determined by changes in intracellular Ca2⫹ or inositol phosphate (12, 133, 241). Bräuner-Osborne et al. (41) observed
that the EC50 for Mg2⫹ significantly decreased (4.7 ⫾ 0.1
to 2.6 ⫾ 0.4 mM), whereas that for Ca2⫹ increased (3.2
⫾ 0.1 to 3.3 ⫾ 0.2 mM) after mutations of Ser147 and
Ser170, which are located in the amino-terminal domain
and are involved in the agonist binding (41). From these
transfection studies of the mutated Ca2⫹/Mg2⫹-sensing
receptor, it has been suggested that discrete but interrelated cation binding sites may be a feature of this receptor
(12). These discrete binding sites remain to be identified,
but it is apparent from these studies that changes in the
extracellular domain of the Ca2⫹/Mg2⫹-sensing receptor
may alter its sensitivity to the various ligands (12). Subtle
changes in the Ca2⫹/Mg2⫹-sensing receptor may significantly affect its selectivity. The present studies with the
endogenous polyvalent cation-sensitive mechanism of the
MDCT cell show that the intracellular signaling is responsive to both extracellular Mg2⫹ and Ca2⫹ and that there
appears to be little interaction between these cations.
Accordingly, the Ca2⫹/Mg2⫹-sensing receptor may function as a Mg2⫹ receptor even in the presence of relatively
high concentrations of extracellular Ca2⫹ (20, 21). The
sites involved in binding Mg2⫹ and Ca2⫹ and the cooperative association in intracellular signaling remain to be
determined (261). Alternatively, the results of our studies
may indicate the presence of separate receptors for extracellular Ca2⫹ and Mg2⫹ in MDCT cells (265). Homologous or heterologous receptor interactions may also modify cation selectivity (14, 15, 258, 229). Again further
research is needed to clarify our understanding of the
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
2⫹
FIG. 11. Concentration dependence of extracellular Mg
([Mg2⫹]o)
or Ca2⫹ inhibition of glucagon-stimulated cAMP. MDCT cells were cultured in DMEM/Ham’s F-12 (1:1) with 0.2% BSA containing 0.6 mM
magnesium and 1.5 mM calcium. At the time of experimentation, the
cells were washed with a buffer solution containing (in mM) 0.5 MgCl2,
1.0 CaCl2, 145 NaCl, 4.0 KCl, 0.8 K2HPO4, 0.2 KH2PO4, 5 glucose, and 20
HEPES-Tris, pH 7. 4. A: to test the effect of [Mg2⫹]o, the buffer solution
was changed to one identical to the above but without MgCl2. This
bathing solution was replaced 10 min later with one containing the
indicated MgCl2 concentrations. B: to test extracellular Ca2⫹ ([Ca2⫹]o),
the cells were initially bathed with the above solutions containing no
CaCl2. This was replaced with one containing the indicated concentrations. Five minutes after the addition of either MgCl2 or CaCl2, glucagon
(10⫺7 M) was added, and cAMP was measured after a 5-min incubation
period. Values are means ⫾ SE for 2 or 3 experiments consisting of 5
individual observations each. *Significance (P ⬍ 0.01) from control
values. [Data from Bapty et al. (21).]
Volume 81
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
65
Ca2⫹/Mg2⫹-sensing receptor and extracellular Mg2⫹ sensing. Regardless of the type of receptor(s) present in the
DCT, Ca2⫹/Mg2⫹ sensing plays an important role in modulating hormone-mediated control of Mg2⫹ transport in
this tubular segment.
A. Ca2ⴙ/Mg2ⴙ Sensing Modulates Peptide Hormone
Responses at the Receptor Level
2⫹
2⫹
FIG. 12. Summary of the effects of Mg /Ca -sensing mechanism
activation on PTH-stimulated cAMP formation and Mg2⫹ uptake. cAMP
was measured by radioimmunoassay, and Mg2⫹ uptake, d([Mg2⫹]i)/dt,
was determined with 1.5 mM extracellular Mg2⫹ in the absence and
presence of neomycin (50 ␮M) as indicated. Neomycin was added 5 min
before the addition of PTH (10⫺7 M) and MgCl2 (1.5 mM). The Mg2⫹
uptake rate was determined over the initial 500 s after addition of PTH.
Values are means ⫾ SE for 3–5 cells. *Significance (P ⬍ 0.001) of Mg2⫹
uptake from respective control values. ⫹Significance (P ⬍ 0.001) of
cAMP determinations from respective control values.
2⫹
FIG. 13. Glucagon stimulation of Mg
uptake is dependent on the
concentration of extracellular Mg2⫹. Mg2⫹ uptake was measured with
and without glucagon (10⫺7 M) in the presence of the extracellular
MgCl2 concentrations as indicated. Inset: change of hormone-stimulated
Mg2⫹ uptake as a function of extracellular Mg2⫹ concentration used to
perform the uptake studies. Values are means ⫾ SE. *Significance (P
⬍ 0.05) from control values not treated with glucagon. [Data from Bapty
et al. (20).]
distal tubule of hypercalcemic and hypermagnesemic
parathyroid gland-intact rats, inferring that magnesium
reabsorption is diminished with elevation of extracellular
Ca2⫹ and Mg2⫹ concentrations. We perfused superficial
distal tubules of TPTXed rats with buffer solutions containing variable calcium and magnesium concentrations.
As indicated above, net calcium and magnesium reabsorption was dependent on electrolyte delivery to this segment as the fractional reabsorption remained constant at
59 ⫾ 3 and 34 ⫾ 5%, respectively (248, 252, 254). However,
when these studies were performed on hypermagnesemic
(plasma magnesium, 3.6 ⫾ 0.2 mM) and hypercalcemic
(plasma calcium, 4.2 ⫾ 0.04 mM) rats, the fractional absorption of magnesium was significantly decreased 6 ⫾ 3
and 14 ⫾ 7%, respectively (246, 254). Similar findings were
observed with calcium absorption in the distal tubule
(246, 254). It is apparent from these studies that plasma
Mg2⫹ and Ca2⫹ control distal absorption of both calcium
and magnesium. Our initial studies also showed that significant elevation of luminal magnesium concentration is
also associated with diminished fractional magnesium
absorption, 24 ⫾ 2% (see elevated luminal Mg2⫹ concentrations of Fig. 4; data from Ref. 254). Although immunocytochemistry demonstrates that Ca2⫹/Mg2⫹-sensing receptors are located on the basolateral membrane (266),
these results suggest that there are Mg2⫹/Ca2⫹-sensing
receptors on the apical or luminal membrane as well.
These recent findings demonstrate an additional receptormediated process that is involved with regulation of magnesium reabsorption in the DCT (136).
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
Activation of the MDCT Ca2⫹/Mg2⫹-sensing receptor
with polyvalent cations, such as neomycin, Mg2⫹, or Ca2⫹,
abolished PTH-, calcitonin-, glucagon-, and AVP-stimulated cAMP accumulation (Fig. 11). Moreover, activation
of Mg2⫹/Ca2⫹ sensing inhibits hormone-stimulated Mg2⫹
uptake into MDCT cells (20). Figure 12 illustrates the
effect of neomycin, a polyvalent cation, on PTH-mediated
cAMP formation and Mg2⫹ entry. Accordingly, hormonemediated Mg2⫹ uptake is dependent on the prevailing
extracellular cation concentrations. To test this notion,
we determined the magnesium concentration dependence
of Mg2⫹ uptake rates with and without glucagon (Fig. 13).
Glucagon stimulated Mg2⫹ uptake in MDCT cells at extracellular Mg2⫹ concentrations below ⬃1.5 mM; concentrations above these levels lead to inhibition of hormonemediated transport. These recent observations with
established cell lines are consistent with earlier micropuncture and microperfusion studies of intact distal
tubules. Le Grimellec et al. (177, 178) reported that distal
magnesium delivery was significantly enhanced along the
66
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
Volume 81
B. Ca2ⴙ/Mg2ⴙ Sensing Modulates Steroid Hormone
Responses at the Transcriptional Level
2⫹
FIG. 14. Extracellular Ca
inhibits 1,25(OH)2D3-stimulated Mg2⫹
uptake through activation of the Ca2⫹/Mg2⫹-sensing receptor. MDCT
cells were Mg2⫹-depleted for 16 h and incubated with a Ca2⫹/Mg2⫹sensing receptor mouse monoclonal antibody (ADD, 98) for 1–2 h. These
cells were treated with 1,25(OH)2D3 (10⫺7 M) with and without 5.0 mM
CaCl2 where indicated, and Mg2⫹ uptake was performed with microfluorescence. The Mg2⫹ uptake rate was determined over 500 s after addition of 1.5 mM MgCl2. Values are means ⫾ SE for 3–5 cells. *Significance
(P ⬍ 0. 05) from control values.
bated the cells with a specific antibody, ADD (98), to the
receptor protein before treating them with high Ca2⫹ and
1,25(OH)2D3 (Fig. 14). The antibody prevented the effect
of Ca2⫹ on 1,25(OH)2D3-induced Mg2⫹ uptake, clearly
demonstrating a receptor-mediated response (Ritchie et
al., unpublished observations). Accordingly, excess
1,25(OH)2D3 increases distal Ca2⫹ and Mg2⫹ transport
leading to elevated serum concentrations and activation
of Ca2⫹/Mg2⫹ sensing that provides a negative feedback
on divalent cation reabsorption.
C. Ca2ⴙ/Mg2ⴙ Sensing Modulates Other
Hormone Responses
The Ca2⫹/Mg2⫹-sensing mechanism has significant
effects on the responses of other hormones. Elevation of
extracellular Ca2⫹/Mg2⫹ also completely inhibited PGE2
stimulation of Mg2⫹ uptake in MDCT cells but marginally
decreased PGE2-mediated cAMP (69). Hartle et al. (132)
have reported that polyvalent cations inhibit PGE1-stimulated cAMP production in MC3T3-E1 osteoblasts. Accordingly, elevation of extracellular Mg2⫹ and Ca2⫹ may
have important effects on prostaglandin actions in many
cell types including the renal epithelium. To determine if
activation of Ca2⫹/Mg2⫹ sensing alters insulin actions, we
pretreated MDCT cells for 5 min with neomycin before
the addition of insulin and MgCl2. Neomycin did not affect
insulin-mediated cAMP formation but diminished insulin-
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
The Ca2⫹/Mg2⫹-sensing receptor modifies steroid
hormone responses at the transcriptional level as well as
at the level of receptor-coupled signaling. Elevation of
extracellular Ca2⫹ or Mg2⫹ inhibits aldosterone potentiation of peptide hormone (PTH, calcitonin, glucagon, and
AVP)-stimulated intracellular cAMP formation in MDCT
cells (20, 21). The acute cellular action of Ca2⫹/Mg2⫹
sensing is through stimulation of G␣i proteins, decreased
receptor-mediated adenylate cyclase activity, and diminished cAMP levels as reviewed above (21). However, we
have evidence that elevated extracellular Ca2⫹ and Mg2⫹
may also inhibit adrenocorticoid responses at the transcriptional level. Actinomycin and cycloheximide, inhibitors of protein synthesis, abolish aldosterone potentiation
of PTH-stimulated cAMP release and Mg2⫹ uptake, providing evidence for transcriptional involvement. The
prominent mechanism of steroids, which operate through
nuclear receptors, is to control transcriptional regulation,
expression, and posttranslational targeting of heterotrimeric G proteins (218). Changes in the levels of expression of G protein subunits in adrenalectomized animals
reflect changes in subunit mRNA, suggesting that adrenocorticoids activate genes encoding G␣s, G␣i, G␤, G␥, and
phospolipase C (PLC)-␤. Adrenal steroids may also increase adenylate cyclase signaling, in the absence of
changes in G␣s, and G␣i, suggesting regulation of the
expression of the adenylate cyclase itself (218). In a recent study, we show that incubation of MDCT cells with
high extracellular Ca2⫹ with the aldosterone inhibits aldosterone-potentiated PTH-induced cAMP formation and
Mg2⫹ uptake (Ritchie et al., unpublished observations).
The evidence indicates that chronic Ca2⫹/Mg2⫹ sensing
inhibits transcriptional/translational processes involved
in the expression of new G protein subunits. The mechanisms by which the Ca2⫹/Mg2⫹-sensing receptor communicates with the nuclear machinery is not known. These
studies strongly support the notion that elevated extracellular divalent cations can modulate expression of mineralocorticoid-dependent G proteins (transcriptional
level) involved with magnesium transport as well as directly controlling PTH-mediated (receptor level) magnesium transport.
As reviewed above, vitamin D metabolites enhance
Mg2⫹ uptake in MDCT cells through a genomic mechanism involving transcriptional/translational processes requiring 3– 4 h after addition of the hormone (Ritchie et al.,
unpublished observations). Elevation of extracellular
Ca2⫹ mitigates 1,25(OH)2D3 stimulation, indicating that
the Ca2⫹/Mg2⫹-sensing receptor may modify gene expression in MDCT cells (Fig. 14). To determine if elevated
extracellular Ca2⫹ inhibited 1,25(OH)2D3 responses
through the Ca2⫹/Mg2⫹-sensing receptor, we preincu-
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
stimulated Mg2⫹ uptake (77). The mechanisms by which
the Ca2⫹/Mg2⫹-sensing receptor inhibits insulin actions
remain undefined. The Ca2⫹/Mg2⫹-sensing receptor is
coupled to G␣i and G␣s proteins that may interact with
insulin-mediated signaling pathways (20, 21). It is now
clear that Ca2⫹/Mg2⫹ sensing plays a significant role in
modifying hormone-mediated Mg2⫹ transport within
MDCT cells.
VII. INTRINSIC CONTROL OF MAGNESIUM
TRANSPORT IN THE DISTAL
CONVOLUTED TUBULE
product of MRG may be important in adaptation of cells
to Mg2⫹ levels. In summary, these studies with isolated
distal cells support the notion of intrinsic controls within
the cells that adapt their magnesium transport rate appropriately to the environmental magnesium (250). We postulate that this intrinsic adaptation provides the discriminatory control of magnesium transport independent of
sodium and calcium. Intrinsic adaptation provides the
selective control that hormonal regulation does not have.
VIII. DISTAL DIURETICS THAT ENHANCE
MAGNESIUM ABSORPTION IN THE
DISTAL CONVOLUTED TUBULE
A. Amiloride
A large number of clinical studies have led to the
notion that amiloride possesses magnesium-conserving
properties in addition to its natriuretic and potassiumsparing effects (48, 251, 340). Despite these observations,
very few experimental studies have been published concerning amiloride effects on renal magnesium handling.
Devane and Ryan (81) have shown that infusion of amiloride reduced the fractional excretion of magnesium in
anesthetized rats, which they attributed to a direct renal
action of the drug (81). The nephron segments and cellular mechanisms were not delineated in this study.
We determined the cellular effects of amiloride on
Mg2⫹ uptake in isolated MDCT cells (76). Amiloride stimulated nifedipine-sensitive Mg2⫹ influx by 41 ⫾ 3% (Fig.
2⫹
2⫹
FIG. 15. Activation of Mg /Ca
sensing does not alter amiloridestimulated Mg2⫹ uptake. Mg2⫹ uptake, d([Mg2⫹]i)/dt, was performed in
the presence of 1.5 mM MgCl2 with or without 10 ␮M amiloride. Neomycin (50 ␮M) was added where indicated 5 min before the addition of
amiloride. Values are means ⫾ SE for 3– 6 cells. *Significance (P ⬍ 0.01)
from control values. There were no significant changes between the
values with amiloride and those with neomycin plus amiloride. [Data
from Bapty et al. (20).]
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
In addition to hormone and Mg2⫹/Ca2⫹-sensing receptor controls described in sections V and VI, the distal
tubule is able to regulate Mg2⫹ uptake in response to
diminished extracellular magnesium (298). Dietary magnesium restriction or intestinal magnesium malabsorption
is associated with enhanced renal magnesium reabsorption and decreased magnesium excretion (89, 250, 302).
Micropuncture studies showed that the increase in magnesium conservation was due to enhanced reabsorption
within the distal tubule (252, 298). Distal calcium and
sodium reabsorption were not affected. Isolated distal
tubule cells, either Madin-Darby canine kidney (MDCK)
or MDCT, cultured in magnesium-free media increase
their Mg2⫹ transport rate as determined by microfluorescence. This response is rapid (within 1–2 h) and specific
for magnesium because there was no effect on sodium or
calcium transport (76, 253). The “adaptation” of magnesium transport rates is intrinsic because there were no
hormones in the culture media (Fig. 1). Furthermore, the
adaptation was dependent on the concentration of media
magnesium and the length of time in the culture media.
Pretreatment of the MDCT cells with cycloheximide inhibited this adaptation by ⬃50% (unpublished observations). Accordingly, it was concluded that magnesium
transport is controlled by gene(s) that somehow respond
to extracellular magnesium. Other genetically controlled
mechanisms involved in intrinsic regulation of magnesium uptake remain to be identified. PCR-differential display identified one gene (termed the magnesium-responsive gene, MRG) that was upregulated by Mg2⫹ depletion
(271). Upregulation was evident after 30 min and maximum (20-fold increase) after 4 h. Readdition of magnesium to Mg2⫹-depleted cells resulted in the return of MRG
levels to control levels within 4 h. MRG upregulation was
specific to Mg2⫹ depletion because Ca2⫹, K⫹, and phosphate depletion of MDCK cells failed to upregulate the
MRG (272). A 15-bp antisense oligodinucleotide (ODN)
complementary to the MRG inhibited Mg2⫹ entry into
Mg2⫹-depleted MDCK cells (48 ⫾ 10 nM/s) compared with
cells transfected with randomized noncomplementary
ODNs (231 ⫾ 15 nM/s). The results suggest that the gene
67
68
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
15). Amiloride was also associated with hyperpolarization
of the membrane voltage by ⫺28 ⫾ 8 mV (111, 303).
Because amiloride does not stimulate Mg2⫹ uptake in the
absence of a change in voltage, we conclude that this
diuretic acts through hyperpolarization of the membrane
voltage (76). As expected, activation of extracellular
Mg2⫹/Ca2⫹ sensing does not influence amiloride-stimulated Mg2⫹ uptake (Fig. 15). These findings provide the
basis for both clinical and experimental observations that
show that amiloride has magnesium-conserving properties (50, 81, 220, 339).
B. Chlorothiazide
dent fashion. Maximal concentrations (10⫺4 M) of chlorothiazide increased Mg2⫹ transport by 58% (70). This was
associated with hyperpolarization of the plasma membrane voltage from ⫺65 ⫾ 5 to ⫺80 ⫾ 5 mV. Inhibition of
Na⫹-Cl⫺ cotransport leading to diminished intracellular
sodium and chloride concentration results in hyperpolarization of the apical membrane of the DCT (67, 316, 329)
and MDCT cells (115). An increase in the membrane
voltage enhances Mg2⫹ uptake into MDCT cells (Fig. 2).
Accordingly, chlorothiazide appears to stimulate Mg2⫹
transport through changes in the membrane voltage similar to that seen with amiloride. These studies with MDCT
cells demonstrate that chlorothiazide enhances Mg2⫹ entry in DCT cells that may be translated into an increase in
magnesium reabsorption and diminished urinary magnesium excretion.
IX. FAMILIAL DISORDERS AFFECTING DISTAL
MAGNESIUM TRANSPORT
Familial diseases, resulting from single gene mutations, are interesting because they demonstrate the phenotypic diversity of transport physiology (Table 2). Moreover, the variation of genetic diseases suggests ways of
magnesium transport that have not been heretofore envisioned. An example of the application of genetic studies
to the clarification of our understanding of renal magnesium handling is the recent investigations of the familal
disease “hypomagnesemia associated with hypercalciuria
and nephrocalcinosis” (HHN). This disease is an autosomal recessive disorder that presents early in childhood. It
is characterized by severe renal magnesium wasting resulting in persistent hypomagnesemia and marked hypercalciuria leading to nephrocalcinosis (198, 212, 223, 224,
269, 325, 328). Through linkage studies, Simon et al. (308)
have identified the gene responsible for this disease. This
gene termed “paracellin-1” or “claudin 16” encodes a protein of 305 amino acids that is a member of the claudin
family comprising proteins such as occludins that form
TABLE 2. Familial disorders affecting distal
magnesium transport
Hypomagnesemia associated with abnormal renal NaCl transport
Gitelman syndrome
Inherited disorders associated with abnormal extracellular Mg2⫹/Ca2⫹
sensing
Autosomal dominant hypoparathyroidism
Familial hypocalciuric hypercalcemia and neonatal severe
hyperparathyroidism
Primary inherited disorders of distal magnesium transport
Hypomagnesemia with secondary hypocalcemia
Infantile primary hypomagnesemia with autosomal dominant
inheritance
Infantile primary hypomagnesemia with autosomal recessive
inheritance
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
A number of experimental studies have suggested
that acute administration of chlorothiazide decreases urinary magnesium excretion relative to the diuretic effects
of increased sodium excretion. Duarte (86) acutely administered chlorothiazide to parathyroid-intact dogs undergoing a diuresis. Fractional excretion of sodium
(FENa) markedly increased from 1.3 to 7.9%, but the fractional excretion of magnesium (FEMg) remained unchanged, 7.3%, after chlorothiazide administration. In
these studies, fractional calcium excretion (FECa) increased from 1.5 to 3.1%. Relative to the FENa, magnesium
excretion fell sixfold from 5.6 to 0.9, and calcium excretion decreased from 1.2 to 0.4 after chlorothiazide administration. Eknoyan et al. (90) confirmed these studies and
attributed the observation of marked natriuresis and modest magnesiuria and calciuria to the differential reabsorption of these cations in the loop and distal tubule. These
studies suggest that chlorothiazide may increase tubular
reabsorption of magnesium relative to the natriuretic effects. We performed clearance and micropuncture studies
in TPTXed dogs (257). The acute administration of chlorothiazide resulted in a relatively greater increase in FENa
from 0.5 to 5.6% than calcium (FECa/FENa increased from
1.3 to 1.9) or magnesium (FEMg/FENa fell from 1. 4 to 1.3).
Similar results were also observed in TPTXed hamsters,
where FENa increased from 1.0 to 3.4% while FECa/FENa
decreased from 22.7 to 5.0 and FEMg/FENa fell from 19.3 to
5.0 (347). Micropuncture experiments demonstrated that
this action occurred along the distal tubule. Micropuncture studies of the hamster have also shown that chlorothiazide increases magnesium reabsorption relative to sodium in the distal tubule (345). Accordingly, the acute
administration of chlorothiazide produces a significant
natriuresis together with little or no change in urinary
calcium or magnesium excretion. The results of these
studies clearly demonstrate a divergence of sodium absorption with calcium and magnesium transport within
the DCT.
Studies with isolated MDCT cells have shown that
chlorothiazide increases Mg2⫹ uptake in a dose-depen-
Volume 81
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
A. Hypomagnesemia Associated With Abnormal
Renal NaCl Transport
Gitelman syndrome and Bartter syndrome are two
autosomal recessive disorders of renal electrolyte transport that have been associated with hypokalemia due to
renal potassium loss, chloride-resistant metabolic alkalosis, and elevated plasma renin and aldosterone levels but
normal blood pressure (24, 124). The cellular basis for
Gitelman and Bartter syndromes is diminished NaCl absorption in the distal tubule and Henle’s loop, respectively
(307). Renal magnesium wasting and hypomagnesemia is
a distinctive characteristic of Gitelman syndrome,
whereas it is not a common feature of Bartter syndrome
(30, 124, 278).
Bartter syndrome can be distinguished from Gitelman syndrome on the basis of the clinical presentation
and biochemical profile (28, 29, 30, 160, 290, 311, 320,
326 –328). Patients with infantile Bartter syndrome
characteristically present in infancy with a urinary concentrating defect, polyhydramnios, failure to thrive,
and fasting hypercalciuria leading to medullary nephrocalcinosis (80, 280, 338). Those with classic Bartter
syndrome present later in childhood with features of
water and salt depletion, including polydipsia, polyuria,
and episodes of dehydration. Bartter syndrome patients
fail to respond normally to furosemide, suggesting to
investigators that this disease was due to defective loop
function (123, 164, 166, 280, 297). Using family linkage
studies, Simon and co-workers (304 –306) delineated
three genetic defects that form the basis for distinguishing three distinct physiological phenotypes in
these patients (Table 3). Type I Bartter syndrome is due
to defective Na⫹-K⫹-Cl⫺ cotransport (NKCC2 gene)
and characterized by severe hypokalemia in addition to
the above (305). Type II Bartter syndrome is associated
with mutations in a potassium channel (ROMK gene,
30-pS K⫹ channel) activity (305). Because this K⫹ channel is involved in potassium secretion in the CCD,
hypokalemia is less severe in this form of the disease.
The type III Bartter syndrome is based on a mutation of
the basolateral membrane chloride channel (ClCNKB)
(306). Like type I patients, type III patients have severe
hypokalemia, but unlike type I and type II phenotypes,
type III patients usually have normal calcium excretion,
and nephrocalcinosis is not observed. It has been suggested that up to 30% of Bartter patients may have
hypomagnesemia due to renal magnesium wasting (173,
297). However, it is clear that some of these cases
represent a form of Gitelman syndrome, and others
may be another variant of hypokalemic metabolic alkalosis. In addition, hypomagnesemia does not reliably
segregate to any of the three types of Bartter syndrome
defined by molecular studies, suggesting that other circumstances may affect renal magnesium absorption.
Supporting this notion is evidence that magnesium balance is normal in a Na⫹-K⫹-Cl⫺ cotransport knockout
mouse mimicking type I Bartter syndrome (323).
Chronic usage of furosemide is sometimes associated
with hypomagnesemia due to excessive urinary magnesium excretion, but it is not universal (251). Thus it is
not apparent why most individuals with Na⫹-K⫹-Cl⫺
cotransport defects should be comparatively free of
renal magnesium wasting. It may be that the loop and
distal tubule adapts to conserve magnesium in this
disorder as it does for NaCl (156, 157, 190, 285). Bartter
syndrome typifies the serial control of magnesium conservation in the loop and distal tubule. Distal tubular
function compensates for diminished loop absorption
even though the hormonal controls are similar in the
two nephron segments.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
the tight junctions of epithelial paracellular pathways.
Claudin 16 is found in the paracellular regions of medullary and cortical segments of the thick ascending limb and
the DCT. Simon et al. (308) propose that claudin 16 is the
protein involved in controlling magnesium and calcium
permeability of the cortical thick ascending limb. Mutations in this gene presumably result in abnormal permeability of the paracellular pathway leading to decreased
magnesium and calcium reabsorption. These studies explain the earlier microperfusion data of Mandon et al.
(197), who demonstrated that magnesium absorption
within the cortical thick ascending limb was passive and
paracellular in nature so that it is influenced by transepithelial voltage and the permeability of the paracellular
pathway. The permeability of the paracellular pathway is
presumably determined by electrostatic charges of proteins comprising this route (255). De Rouffignac and coworkers (84, 285) have postulated that these paracellular
charge complexes may be influenced by hormones that
regulate magnesium absorption. Accordingly, genetic diseases involving defective claudin 16 expression are associated with diminished magnesium absorption. The recent
work of Simon et al. (308) is a good example of the use of
genetic studies in addressing constitutive and congenital
disturbances of magnesium metabolism to further our
understanding of the physiology of cellular magnesium
transport. These investigations may also lead to other
avenues of research. Claudin 16 comprises the paracellular pathway of the medullary thick ascending limb and the
DCT, but no magnesium is absorbed through the paracellular pathways in these segments. It remains to be determined what physiological role, if any, this protein plays in
these segments. Finally, these observations led to speculation of other proteins that may play a role in paracellular
magnesium absorption.
69
70
TABLE
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
Volume 81
3. Inherited disorders of renal magnesium handling
Disease
Gitelman
Bartter1
Bartter2
Bartter3
Hypomagnesemia, hypercalciuria, and nephrocalcinosis
Hypomagnesemia and secondary hypocalcemia
Inactivating Ca2⫹/Mg2⫹ sensing “FHH/NSHPT”
Activating Ca /Mg
2⫹
sensing “ADH”
Late-onset, isolated hypomagnesemia
Late-onset, isolated hypomagnesemia
Gene
Chromosome
Autosomal
Recessive
Autosomal
Recessive
Autosomal
Recessive
Autosomal
Recessive
Autosomal
Recessive
Autosomal
Recessive
Autosomal
Dominant
Autosomal
Dominant
Autosomal
Dominant
Autosomal
Recessive
SLC12A3
16q13
NKCC2
15q15-21
ROMK1
11q24
ClCNKB
1p36
PCLN1
CLDN16
?
2q27
Ca2⫹/Mg2⫹-SR
Selectivity
Mg2⫹
263800
600968
241200
600839
600359
601678
602023
Ca2⫹/Mg2⫹
2⫹
OMIM No.
603959
9q12-22.2
Ca /Mg
2⫹
603959
3q13.3-21
Ca2⫹/Mg2⫹
?
11q23
Mg2⫹
601198
601199
601198
601199
154020
?
?
Mg2⫹
248250
2⫹
2⫹
2⫹
Ca /Mg -SR
Ca /Mg
2⫹
Ca2⫹/Mg2⫹-SR, Ca2⫹/Mg2⫹-sensing receptor; FHH, familial hypocalciuric hypercalcemia; NSHPT, neonatal severe hyperparathyroidism; ADH,
autosomal dominant hypoparathyroidism. OMIM no. refers to the Online Mendelian Inheritance in Man database reference number (URL ⫽
http://www3.ncbi.nlm.nih.gov/omim/).
1. Gitelman syndrome
Patients with Gitelman syndrome are not polyuric or
polydipsic but have hypocalciuria and usually show renal
magnesium wasting (236). They often present in late
childhood with a hypokalemic metabolic alkalosis and
low serum magnesium, which may be asymptomatic or
may be severe enough to cause hypomagnesemic tetany
(27, 158, 173). Patients with Gitelman syndrome fail to
respond to chlorothiazide, leading to the prediction that
the renal defect is in the DCT (26, 62, 214, 320). Simon et
al. (309) have shown that Gitelman syndrome families are
genetically linked to a locus at 16q13 and identified causative mutations in the chlorothiazide-sensitive NaCl cotransporter expressed in the DCT (Fig. 16) (309). There
have now been over 82 distinct mutations that are associated with Gitelman syndrome. Nearly all of these mutations are nonconservative and affect amino acids that
have been conserved throughout evolution. Schulteis et
al. (296) developed a mouse model of Gitelman syndrome
by deleting the gene coding for the apical NaCl cotransporter of the DCT. These mice show all the cardinal
features of Gitelman syndrome including renal calcium
conservation and diminished serum magnesium concentrations presumably due to urinary magnesium wasting,
although the latter was not directly determined in this
study. Because chlorothiazide enhances calcium reabsorption in the DCT, the hypocalciuria of Gitelman syndrome is readily explained (278). The reasons for renal
magnesium wasting are unknown (251).
Some of the features of Gitelman syndrome may be
observed in patients chronically receiving thiazide diuret-
ics raising the possibility that loss in Na⫹-Cl⫺ cotransport
could result in this disease. Although renal magnesium
wasting and hypomagnesemia in Gitelman patients remain to be explained, a number of mechanisms may be
invoked. We have shown that cellular potassium depletion diminishes Mg2⫹ uptake in MDCT cells (70, see below). However, potassium deficiency is not always asso-
FIG. 16. Schematic model of inherited disorders of magnesium absorption in the distal convoluted tubule. The bases for the primary
inherited disorders, hypomagnesemia with secondary hypocalcemia
(HSH), infantile hypomagnesemia with autosomal dominant inheritance,
and infantile hypomagnesemia with autosomal recessive inheritance,
are speculative. ADH, autosomal dominant hypoparathyroidism; FHH,
familial hypocalciuric hypercalcemia; NSHPT, neonatal severe hyperparathyroidism.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
2⫹
Inheritance
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
lation with a decrease in DNA synthesis leading to
apoptosis and tubule atrophy (188, 189). Whether diminished cell surface is sufficient to jeopardize magnesium reabsorption within this segment is unknown, but
this is a testable tenant in isolated DCT cells.
B. Inherited Disorders Associated With Abnormal
Extracellular Mg2ⴙ/Ca2ⴙ Sensing
The Ca2⫹/Mg2⫹-sensing receptor plays an important
role in controlling calcium and magnesium transport in
both the loop and the distal tubule (20, 136). Both inactivating and activating mutations of the Ca2⫹/Mg2⫹-sensing
receptor have been described that are now well characterized (241). These abnormalities of Ca2⫹/Mg2⫹ sensing
are not selective for magnesium because calcium is also
similarly affected (Table 3).
1. Familial hypocalciuric hypercalcemia and neonatal
severe hyperparathyroidism
Familial hypocalciuric hypercalcemia (FHH) (9, 169,
175, 201) and neonatal severe hyperparathyroidism
(NSHP) are conditions resulting from inactivating heterozygous and homozygous mutations, respectively (240 –
242). Renal excretion of calcium and magnesium is reduced leading to hypercalcemia and sometimes
hypermagnesemia (9, 169, 175, 201). Defective extracellular Ca2⫹/Mg2⫹ sensing likely leads to inappropriate absorption of calcium and magnesium in both the thick
ascending limb (136, 336) and magnesium transport in the
distal tubule (15, 16). Ho et al. (145) made a Ca2⫹/Mg2⫹sensing receptor knockout mouse that displays many of
the characteristics of FHH and NSHPT patients. Homozygous mutant mice had elevated serum calcium and PTH
concentrations but modest elevations of serum magnesium. The urinary concentration of calcium was inappropriately low given the marked elevations in serum calcium
levels; urinary magnesium was not reported. Careful
clearance studies are warranted to establish renal magnesium wasting because these animals are dehydrated
and underweight. The homozygous mice also had severe
skeletal abnormalities compared with the heterozygous
or control animals (145).
2. Autosomal dominant hypoparathyroidism
Activating mutations termed autosomal dominant hypoparathyroidism (ADH) are dominant and present clinically as isolated hypocalcemic hypoparathyroidism. Hypomagnesemia may be observed in up to 50% of the
patients (227, 234). The mutant parathyroid and kidney
Ca2⫹/Mg2⫹-sensing receptor has a lower set point for
plasma Ca2⫹ and Mg2⫹concentrations so that for any
given divalent cation concentration PTH secretion and
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
ciated with magnesium problems. This is evident in
patients with Bartter’s syndrome. Although all patients
with Bartter’s syndrome have hypokalemia, few have abnormal serum magnesium concentrations. Clearly, hypokalemia does not consistently lead to renal magnesium
wasting. How then do chronic inhibition of Na⫹-Cl⫺ cotransport with thiazides or point mutations in Na⫹-Cl⫺
cotransport within the DCT, as observed in Gitelman’s
patients, lead to renal magnesium wasting? We propose
the following possible explanations. Inhibition of Na⫹-Cl⫺
cotransport results in diminished intracellular Cl⫺, apical
membrane hyperpolarization, enhanced Mg2⫹ entry (63,
115, 303, 312), and elevated cellular Mg2⫹ concentration
(54). Elevated intracellular Mg2⫹ may be perceived by the
DCT cell, resulting in downregulation of distal magnesium
transport leading to urinary magnesium excretion inappropriate for the plasma magnesium concentration (see
sect. VII). Reilly and Ellison (263) have postulated another
way to explain magnesium wasting of Gitelman’s patients
(263). They suggest that the absence of claudin 16 expression may somehow allow magnesium secretion via the
paracellular pathway. The notion is that Gitelman syndrome converts some DCT cells that are predominantly
electroneutral cells to cells that reabsorb Na⫹ in an electrogenic manner. As discussed by these authors, the cells
are also responsive to the actions of aldosterone. Accordingly, the combination of the dominance of electrogenic
ion transport pathways, the stimulation by aldosterone,
and the increased Na⫹ concentration all favor electrogenic Na⫹ reabsorption. This greatly increases the magnitude of the transepithelial voltage that drives magnesium secretion. We do not favor this explanation because
our earlier micropuncture studies failed to detect any
secretion of Mg2⫹ in microperfused distal tubules (246,
254). Furthermore, perfusion of superficial distal tubules
of hypermagnesemia rats with solutions containing sodium sulfate to elevate the transepithelial voltage failed to
elicit luminal Mg2⫹ entry (247). Finally, claudin 16 is
thought to be involved with enhancing Mg2⫹ and Ca2⫹
permeability in the thick ascending limb; accordingly, it
is not evident that the aberrant or absent protein expression would increase permeability, thereby increasing Mg2⫹ back-flux or secretion. As an alternative explanation, Kaissling et al. (156) have reported that
complete block of NaCl entry with thiazide treatment
results in apoptosis of rat DCT (156). The Na⫹-Cl⫺
cotransporter knockout mice of Schultheis et al. (296)
also demonstrated a decrease in number, height, and
basolateral infolding of DCT cells. The mitochondria
was less well developed in the homozygous null mice
compared with the heterozygotes. Additionally, acute
interstitial nephritis has been observed in human subjects chronically using thiazide diuretics (193). It is
postulated that inhibition of Na⫹ entry leads to increased intracellular Ca2⫹ and impaired volume regu-
71
72
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
renal calcium transport are suppressed. The hypomagnesemia is usually asymptomatic, but significant deficiencies have been reported (227). Some of this variability is
due to the heterogeneity of the activating mutations and a
corresponding variability in the set-point detection limit
for serum Ca2⫹ and Mg2⫹ concentrations.
C. Primary Inherited Disorders of Distal
Mg2ⴙ Transport
1. Hypomagnesemia with secondary hypocalcemia
2. Infantile isolated renal magnesium loss
Hypomagnesemia due to late-onset isolated renal
magnesium loss is an autosomal dominant condition
associated with few symptoms other than chondrocalcinosis (121). Patients always have hypocalciuria and
variable, but usually mild, hypomagnesemic symptoms.
Meij et al. (210) have reported that the disorder maps to
chromosome 11q23 in two large Dutch families. Database searches of the linkage region have so far failed to
identify candidate genes, but Meij et al. (210) speculate
from our experimental studies (251) that the mutation
may lie in the distal tubule. Additionally, there is evidence for a variant form hypomagnesemia due to infantile isolated renal magnesium loss that is more consistent with autosomal recessive inheritance. Meij et al.
(personal communication) excluded linkage to any of
the known loci previously reported indicating a novel
disease. The patients also have variable symptoms, but
they usually have normal urinary calcium excretion
(104, 120). Because the epithelial transporters of magnesium have not been delineated, it is unclear at what
level the tubule magnesium absorption is affected.
Clinical observations suggesting both dominant and
recessive inheritance argue for a number of familial renal
wasting diseases. As the distal tubule reabsorbs 10 –15%
of the filtered magnesium (80 –95% of that delivered to it),
one would expect that if the primary reabsorptive channel
were affected, then renal magnesium conservation would
be severely compromised leading to marked hypomagnesemia. Alternatively, there may be separate magnesium
transporters within the distal tubule under separate genetic control. This is a fertile ground for further genetic
studies.
3. Experimental genetic studies
In addition to clinical investigations, experimental
studies are being used to define the genetic basis of
magnesium homeostasis. Henrotte and colleagues
(138 –141) established inbred lines of mice by selecting
for high and low plasma magnesium levels. Mice of the
hypomagnesemic line have inappropriately high urinary
magnesium excretion relative to serum levels (142).
The hypomagnesemic, hypermagnesiuric mice have
normal calcium homeostasis, suggesting a selective tubular defect of magnesium reabsorption. Genetic analysis of these mice indicated that both histocompatibility (H2) related and H2 unrelated to loci were
significant determinants of extracellular and intracellular magnesium content in the mice (142). These mice
are being used by Andre Mazur, Unite Maladies
Metaboliques et Micronutriments, Theix, France, to genotype quantitative traits associated with renal magnesium wasting (personal communication). Studies such
as these will be useful in explaining the clinical observations.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
Hypomagnesemia with secondary hypocalcemia
(HSH) is an autosomal recessive disorder that manifests
in the newborn period and is characterized by very low
serum magnesium and low calcium concentrations (1, 58,
127, 233, 244, 279). Patients usually present before 6 mo of
age with neurological symptoms of hypomagnesemia and
hypocalcemia, including tetany, muscle spasms, and seizures (54, 88). In older children with inadequate control,
clouded sensorium and disturbed speech are often seen,
and choreoathetoid movements have been described. The
hypocalcemia is secondary to parathyroid failure (7, 318)
and peripheral PTH resistance as a result of magnesium
deficiency (314). Hypokalemia is occasionally present
that is only corrected with normalization of plasma magnesium (314). The disease is primarily due to defective
intestinal magnesium absorption and may be fatal unless
treated with high oral intakes (43, 225, 232, 245, 300, 310,
315). Walder et al. (335) reported that HSH is an autosomal recessive disease and showed by genetic linkage
studies that the gene segregates to chromosomes 9 (9q12–
9q22.2). They suggest that the candidate gene codes a
receptor or an ion channel involved in active intestinal
magnesium absorption (335). Because passive intestinal
transport is normal, the disease can be treated by high
oral magnesium supplements. Renal magnesium conservation has been reported to be normal in most studies,
suggesting that the kidney responds appropriately to low
circulating magnesium levels by reabsorbing fractionally
greater amounts of filtered magnesium. In some cases,
however, a renal leak may also be present that manifests
primarily when oral supplements are insufficient to normalize the serum magnesium (207). We speculate that the
renal leak may be due to altered Mg2⫹ entry into DCT
cells. Whether this condition is genetically heterogeneous
remains to be seen, but further studies to address renal
tubular magnesium absorption as a function of plasma
concentration and filtered magnesium in patients with
well-delineated intestinal defects are clearly warranted.
Volume 81
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
X. ACQUIRED DISORDERS THAT DIMINISH
DISTAL MAGNESIUM TRANSPORT
A. Potassium Depletion
FIG. 17. Schematic model of inherited disorders of magnesium absorption in the distal convoluted tubule. The cellular mechanisms of
phosphate depletion, potassium depletion, cyclosporin, and cisplatin are
not known, but the evidence suggests that they affect intracellular
regulatory processes rather than direct effects on Mg2⫹ channels or the
Ca2⫹/Mg2⫹ sensing.
The interrelationships of plasma potassium and magnesium have clinically important ramifications but remain
unexplained. As reviewed by Agus (2), hypokalemia is
commonly associated with hypomagnesemia. The hypokalemia in these patients is difficult to correct with potassium supplementation alone but rapidly responds following correction of the magnesium deficit (341).
Intracellular Mg2⫹ activates or rectifies many K⫹ channels
leading to the speculation that magnesium depletion may
alter potassium reabsorption or potassium secretion
within the distal nephron. It is unlikely that cellular Mg2⫹
would fall sufficiently to diminish Mg-ATP levels so that
luminal ATP-regulated K⫹ channels are probably not involved (2). Again, this notion would appear to be testable
in isolated distal tubule cells.
B. Phosphate Depletion
One of the hallmarks of phosphate depletion is the
striking increase in urinary excretion of calcium and magnesium (202). Magnesium excretion may be sufficiently
large to lead to overt hypomagnesemia. The increase in
divalent ion excretion in both human and experimental
animals occurs within hours after initiation of dietary
phosphate restriction. It is evident from clearance experiments that the urinary excretion of divalent cations of
phosphate-depleted subjects is inappropriate for the
plasma concentration, supporting the notion of defective
tubular transport (60). Using micropuncture, we have
demonstrated that defective magnesium absorption occurred in the loop of Henle and the distal tubule of
phosphate-depleted dogs (347).
We have also shown that cellular phosphate depletion
leads to diminished Mg2⫹ uptake in MDCT cells (71). This
observation supports the notion that the DCT may be involved, in part, in decreased magnesium absorption and
increased magnesium excretion observed with phosphate
depletion. The effects of phosphate depletion on Mg2⫹ uptake in MDCT cells are reminiscent of those observed in the
intact kidney. Removal of phosphate from the media rapidly
leads to diminished Mg2⫹ transport, which is dependent on
the degree of phosphate depletion. Mg2⫹ uptake is inhibited
by 50% when cultured in ⬃0.3 mM phosphate. These actions
are fully reversible with the return of phosphate to the
media. The induction of defective transport that is associated with phosphate depletion must reside within the cell
either to prevent the normal upregulation of Mg2⫹ transport
with Mg2⫹ deficiency or to inhibit Mg2⫹ uptake through
actions on transport processes. To determine if phosphate
depletion acts through posttranslational mechanisms,
MDCT cells were first Mg2⫹ depleted for 16 h to maximally
upregulate Mg2⫹ transport. The cells were then phosphate
depleted for various time periods, and Mg2⫹ uptake was
assessed by microfluorescence (Fig. 18). Phosphate deple-
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
The relationship of cellular potassium and magnesium metabolism is complex and far from understood.
Potassium depletion sometimes results in increased
urinary magnesium and calcium excretion (87, 154, 179,
348). The increase in urinary excretion of divalent cations may be explained by the known effects of potassium depletion on the thick ascending limb of the loop.
Chloride conservation is impaired in potassium-depleted rats, which may be related to altered basolateral
transport resulting in diminished NaCl transport (187).
To date, there is no direct evidence for changes in
magnesium absorption in the thick ascending limb with
potassium depletion. Because magnesium and calcium
are absorbed by passive mechanisms, dependent on
NaCl transport, it is probable that impaired NaCl transport may lead to diminished divalent cation absorption
in this segment (249, 289). Our studies, using isolated
MDCT cells, however, suggest that potassium depletion
may have important effects on magnesium transport
within the DCT (Fig. 17). MDCT cells were cultured in
low potassium, 2.5 mM, for 16 h before determination
of Mg2⫹ uptake (70). Cellular potassium depletion (89
⫾ 5 mM vs. control 126 ⫾ 6 mM) resulted in diminished
Mg2⫹ uptake as determined by microfluorescence. The
cellular mechanisms for the decrease in Mg2⫹ entry
with potassium depletion are not known.
73
74
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
tion resulted in diminished Mg2⫹ uptake in preadapted cells,
which suggests it affects transport through actions on preformed pathways rather than through transcriptional or
translational mechanisms. Further studies are necessary to
define these posttranslational events. Interestingly, phosphate depletion is associated with diminished expression of
the MRG described above (258). Again, the role of MRG in
magnesium reabsorption requires further work to clarify our
understanding of control of cellular transport. It is evident
from these studies with isolated MDCT cells that magnesium
wasting commonly observed in hypophosphatemia and
phosphate depletion could be due, in part, to diminished
Mg2⫹ uptake in the DCT.
C. Acid-Base Changes
It has long been known that systemic acidosis is
associated with renal magnesium wasting (34, 180, 200).
Acute metabolic acidosis produced by infusion of NH4Cl
or HCl leads to significant increases in urinary magnesium
excretion (179, 200). Chronic acidosis also leads to urinary magnesium wasting which, as with acute acidosis,
may be partially corrected by the administration of bicarbonate (181, 235). In contrast to metabolic acidosis, acute
and chronic metabolic alkalosis consistently leads to a fall
in urinary magnesium excretion (346).
Although it has long been known that metabolic acidosis and alkalosis alter renal magnesium handling, relatively little information is available regarding the tubular
segments involved. Wong et al. (344) showed that meta-
bolic alkalosis resulted in increased magnesium reabsorption in the distal tubule of the dog. Magnesium reabsorption was closely associated with bicarbonate delivery to
the distal tubule in this study. We have shown that acute
bicarbonate infusions into chronic acidotic rats lead to a
marked increase in magnesium reabsorption in the loop
of Henle and distal tubule (301). Thus, on balance, the
evidence is that metabolic acidosis and alkalosis act on the
distal tubule to change renal magnesium conservation.
We have used the MDCT cell line to determine the
direct effects of proton changes on cellular Mg2⫹ uptake
(72). Unlike previous reports, this approach has the advantages of isolating the direct cellular effects of H⫹ on Mg2⫹
transport in a controlled fashion that is independent of
extrarenal influences. The results of these experiments
show that elevation of pH markedly enhances Mg2⫹ uptake,
whereas acidosis significantly diminishes transport (72). The
studies with isolated MDCT cells, where we could carefully
control pH values and bicarbonate concentrations, clearly
show that bicarbonate does not directly alter Mg2⫹ uptake
(72). This information indicates that protons affect Mg2⫹
entry through changes in intracellular pH or directly affects
the Mg2⫹ transport pathway. A change in extracellular pH
has significant effects on many kinds of ion channels. For
example, Chen et al. (56) postulated that protonation of
glutamates within the Ca2⫹ pore of L-type Ca2⫹ channels
blocks the permeation pathway. We envision that protonation of the Mg2⫹ pathway may alter Mg2⫹ influx leading to
diminished transport. This would have significant effects on
distal magnesium absorption, leading to renal magnesium
wasting with metabolic acidosis.
Poorly controlled diabetes mellitus is often associated
with metabolic acidosis. Hypomagnesemia has been reported in ⬃25% of diabetic patients, and renal magnesium
wasting has been associated with both type I and type II
diabetes mellitus (152, 162). Because insulin stimulates magnesium conservation in the loop (195) and distal tubule (68),
insulin deficiency could explain the increase in urinary magnesium excretion. A number of indirect influences commonly present in diabetes mellitus may also explain an
increase in magnesium excretion. First, uncontrolled hyperglycemia and hyperglycuria may increase excretion through
osmotic diuresis (251). Second, metabolic acidosis commonly observed in diabetes may increase magnesium excretion by its actions within the distal tubule (251). Finally,
hypophosphatemia and hypokalemia are often associated
with diabetes; both may decrease distal magnesium reabsorption (152). Acidosis with any one of these entities may
underlie the diminished magnesium reabsorption and hypomagnesemia commonly observed in diabetes mellitus.
D. Cytotoxic Agents
The use of a number of antibiotics, tuberculostatics,
and antiviral drugs (3, 158, 299) may be associated with
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
2⫹
FIG. 18. Phosphate depletion inhibits Mg
uptake in MDCT cells
preadapted to low magnesium. MDCT cells were cultured in zero magnesium, normal phosphate media for 16 h and for another 16 h in either
zero phosphate or 1.0 mM phosphate in addition to zero magnesium.
Mg2⫹ uptake was assessed in both cell populations according to the
methods given in Fig. 1 using 1.5 mM MgCl2 in the refill solution. Values
are means ⫾ SE. *Significance (P ⬍ 0.05) from control. [Data from Dai
et al. (71).]
Volume 81
DISTAL TUBULE MAGNESIUM TRANSPORT
January 2001
renal magnesium wasting (Table 4). The cellular basis by
which some of these agents lead to diminished magnesium transport has recently become clear, but others
remain unexplained. Many are associated with general
cellular toxicity and associated electrolyte abnormalities,
but it is of interest that some are relatively selective for
magnesium.
75
effects of cisplatin may persist months or years later, long
after the inorganic platinum has disappeared from the renal
tissue (199, 334). Whatever cellular mechanisms are involved, it must include genetic alteration of magnesium
transport. The fact that cisplatin exerts its therapeutic effects by binding cellular DNA may be relevant (294).
2. Aminoglycosides
1. Cisplatin
TABLE 4. Acquired disorders affecting distal
magnesium transport
Potassium depletion
Phosphate depletion
Metabolic acidosis
Cytotoxic agents
Cisplatin
Cyclosporin, FK506
Aminoglycosides
Gentamicin
Streptomycin
Neomycin
Tobramycin
Amikacin
Tuberculostatics
Capreomycin
Viomycin
Amphotericin B
Pentamidine
Aminoglycosides, such as gentamicin, cause hypermagnesiuria and hypomagnesemia (Table 4). As many as 25% of
patients receiving gentamicin will present with hypomagnesemia (299). The hypermagnesiuric response occurs soon
after the onset of therapy; it is dose dependent and readily
reversible upon withdrawal (94, 122, 230, 237). Hypokalemia
is frequently observed with the magnesium deficiency. Magnesium wasting is associated with hypercalciuria that may
lead to diminished plasma calcium concentrations (94, 161).
This would suggest that aminoglycosides affect renal magnesium and calcium transport in the tubular segments where
both are reabsorbed, namely, the thick ascending limb and
the DCT. Experimental studies with animals support this
notion (4, 103, 112, 231). The cellular mechanisms are unknown, but hypermagnesiuria and hypercalciuria are observed in the absence of histopathological changes (337).
Gentamicin is a polyvalent cation so that it may have its
effects on the Ca2⫹/Mg2⫹-sensing receptor. Activation of this
receptor by polyvalent cations inhibits passive absorption of
magnesium and calcium in the loop and active hormonemediated transport in the DCT (20, 21, 136). In support of
this notion, we have shown that gentamicin inhibits PTHmediated cAMP formation and PTH-stimulated Mg2⫹ uptake
in MDCT cells (159). The inhibition was concentration dependent and reversed by the application of high concentrations of 8-bromo-cAMP or forskolin. We infer from these
studies that gentamicin inhibits hormone-stimulated Mg2⫹
absorption in the DCT that contributes to renal magnesium
wasting, which is frequently observed with the clinical use of
aminoglycosides.
3. Cyclosporin and FK506
The immunosuppressants, cyclosporin and FK506,
commonly lead to renal magnesium wasting and hypomagnesemia (23, 171, 273). Unlike the other agents, these
drugs usually cause a significant reduction in glomerular
filtration rate (GFR) (up to 60%) and modest hypercalcemia and hypokalemia (273). The hypomagnesemic effect
is probably attenuated by the fall in GFR and reduction in
filtered magnesium, but this defect appears to be specific
for magnesium (260, 274, 343). The distal tubule is probably the site of the tubular magnesium leak. It is not
known whether these drugs act through calcineurin,
which is the intracellular receptor for these agents.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
Treatment with the cancer antimetabolite cisplatin
commonly results in renal magnesium wasting and hypomagnesemia (3, 158, 299). The incidence of magnesium deficiency is ⬎30% but increases to ⬎70% with longer cisplatin
usage and greater accumulated doses. Interestingly, cisplatin-induced magnesium wasting is relatively selective (25).
Hypocalcemia and hypokalemia may be observed but only
with prolonged and severe magnesium deficiency (125, 191,
198, 209, 321). The influence of magnesium deficiency on
PTH secretion and end-organ resistance is the likely explanation for enhanced urinary calcium excretion and diminished mobilization resulting in low plasma calcium concentrations (7, 96). The effects on potassium balance are more
difficult to explain. The hypokalemia observed with magnesium deficiency is refractory to potassium supplementation
(275). Cisplatin results in proximal tubular damage, but the
evidence from both clinical and experimental studies indicates that the drug acts on distal tubular magnesium transport (194, 209, 322). Because there is no magnesium reabsorption within the CCD, it is likely that actions within the
DCT are responsible for the renal magnesium leak. Using
micropuncture, Mavichak et al. (209) showed that magnesium reabsorption was diminished in the distal tubule of rats
receiving cisplatin. The cellular mechanisms for the apparent selective effects on magnesium remain undefined. It
would be of interest to determine if amiloride retains its
magnesium-conserving actions in these patients (251). The
76
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
XI. SUMMARY: FUTURE DIRECTIONS IN
RESEARCH OF MAGNESIUM TRANSPORT
IN THE DISTAL CONVOLUTED TUBULE
through activation of an extracellular Ca2⫹/Mg2⫹-sensing
mechanism. Selective control of Mg2⫹ uptake and absorption appears to occur after magnesium restriction. Our evidence suggests that this is through an increase in selective
Mg2⫹ transport, in part, by transcriptional-translational processes involving de novo protein synthesis. Adaptation to
magnesium restriction is observed at both the organ and
cellular levels. The mechanisms used by the DCT cell to
sense the extracellular Mg2⫹ concentration and appropriately adapt the transport rates are fertile areas for future
research. Mg2⫹ uptake may also be modulated by a number
of posttranslational events. Amiloride and chlorothiazide are
magnesium-conserving diuretics by virtue of their ability to
stimulate voltage-sensitive Mg2⫹ entry in DCT cells. A number of inherited diseases affect magnesium transport within
the DCT. These include those associated with abnormal
NaCl absorption (Gitelman syndrome), extracellular Ca2⫹/
Mg2⫹ sensing (FHH and NSHPT), and primary magnesium
wasting most likely affecting selective cellular Mg2⫹ transport. Genetic studies are interesting because they describe
nature’s experiments in control of magnesium transport and
lead to here-to-unforeseen transport possibilities. A large
number of acquired disorders affect magnesium absorption
in the DCT. Cellular potassium depletion diminishes Mg2⫹
transport through undefined ways. As marked increases in
Mg2⫹ concentration or hyperpolarization do not normalize
transport, it is probable that the effect of potassium depletion is on the magnesium transporter. Similarly, cellular
phosphate depletion decreases Mg2⫹ uptake in MDCT cells.
Again, the mechanisms are not known but must be posttranslational because removal of phosphate rapidly leads to
diminished Mg2⫹ uptake in cells that have previously been
fully adapted. Both of these conditions, potassium and phosphate depletion, lead not only to diminished Mg2⫹ uptake in
the DCT but to renal magnesium wasting, supporting the
notion that the defect in DCT transport provides the basis
for these diseases. Our studies suggest that cellular potassium and phosphate depletion act through different mechanisms. Acid-base changes alter cellular Mg2⫹ uptake and
renal magnesium reabsorption. These changes are due to
direct effects of protons on Mg2⫹ transport and are independent of alterations in membrane voltage and modulations
due to potassium and phosphate depletion. Again, metabolic
alkalosis or acidosis may play a significant role in dictating
the control of renal magnesium handling. Magnesium wasting and hypomagnesemia are common observations in metabolic acidotic patients. Because these three entities, potassium depletion, hypophosphatemia, and metabolic acidosis,
act at different sites along the Mg2⫹ transport pathway, they
may exacerbate renal magnesium wasting when present in
combination. Finally, various drugs including antibiotics,
antitumor agents, and immunosuppressants may affect magnesium handling out of proportion to other electrolytes.
Areas for future research include electrophysiological definition of Mg2⫹ entry into epithelial cells, molecular identifi-
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
Although the majority of filtered magnesium is reabsorbed in the thick ascending of the loop of Henle, it is
apparent that the distal tubule also participates in the
sensitive and selective control of renal magnesium handling. It also serves an important site for familial and
acquired magnesium wasting disorders. As with other
cations, such as sodium, potassium, and calcium, the
distal tubule plays a significant role in control of daily
electrolyte balance and perhaps more importantly in homeostasis over a long period of time. The DCT may reabsorb a minor fraction of filtered salt, but it provides an
additional regulation that is serially posed to act in concert with the other nephron segments to affect electrolyte
homeostasis. The aim of this review has been to review
our current understanding of magnesium handling by the
distal tubule and to integrate these observations into the
overall renal control of magnesium. Like other cations,
the reabsorptive rate of magnesium in the distal tubule is
load dependent; that is, absolute magnesium absorption
increases with enhanced delivery to this segment. This
association is valid whether magnesium delivery is altered either by an increase in tubule fluid magnesium
concentration or by an increase in fluid flow rate issuing
from the loop of Henle. Transepithelial magnesium absorption is active in the distal tubule as transport is
against luminal-to-interstitial electrical and concentration
gradients. The evidence is that Mg2⫹ moves across the
apical membrane dependent on the transmembrane concentration and down a favorable electrical gradient. Accordingly, this transport is passive and likely through a
selective Mg2⫹ channel. The mechanism whereby Mg2⫹
exits across the basolateral membrane into the interstitium is unknown but must be active. The rate-limiting step
and the site of regulation appears to occur with the entry
of Mg2⫹ into the DCT cell. The peptide hormones, PTH,
calcitonin, glucagon, and AVP, increase Mg2⫹ transport in
the distal tubule through cAMP-, phospholipase C-, and
protein kinase C-mediated signaling pathways. PGE2 and
isoproterenol increase Mg2⫹ entry into MDCT cells by
unknown means. Aldosterone potentiates hormone-stimulated cAMP release and Mg2⫹ uptake in MDCT cells.
1,25(OH)2D3 enhances Mg2⫹ uptake via intracellular pathways that are independent of cAMP-protein kinase A and
additive to the actions of peptide hormones such as PTH.
Insulin stimulates Mg2⫹ uptake, but its role in renal magnesium balance is not fully understood. Further studies are
needed to clarify our understanding of the cellular events
involved with magnesium transport and to describe the integrated actions of these important peptide and steroid hormonal controls. Hypercalcemia and hypermagnesemia inhibit hormone-stimulated cAMP release and Mg2⫹ uptake
Volume 81
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
cation of Mg2⫹ transport pathways, and description of the
controlling mechanisms regulating Mg2⫹ transport such as
transcriptional processes involving the magnesium response
element. Finally, cellular magnesium handling remains to be
studied in distal segments other than the DCT. Mechanisms
and controls of Mg2⫹ uptake in connecting tubule and the
initial collecting tubule may differ from those described for
the DCT.
15.
16.
17.
18.
19.
20.
21.
22.
REFERENCES
23.
1. ABDULRAZZZAQ YM, SMIGURA FC, AND WETTRELL G. Primary infantile
hypomagnesaemia: report of two cases and review of literature.
Eur J Pediatr 148: 459 – 461, 1989.
2. AGUS ZA. Hypomagnesemia. J Am Soc Nephrol 10: 1616 –1622, 1999.
3. AL-GHAMDI SMG, CAMERON EC, AND SUTTON RAL. Magnesium deficiency: pathophysiologic and clinical overview. Am J Kidney Dis
24: 737–752, 1994.
4. ALI BH, ABDEL GAYOUM AA, AND BASHIR AA. Gentamicin nephrotoxicity in rats: some biochemical correlates. Pharmacol Toxicol 70:
419 – 423, 1992.
5. AMLAL H, WANG Z, AND SOLEIMANI M. Potassium depletion downregulates chloride-absorbing transporters in rat kidney. J Clin Invest
101: 1045–1054, 1998.
6. ANAST CS AND GARDNER DW. Magnesium metabolism. Disorders
Miner Metab 3: 424 –506, 1981.
7. ANAST CS, WINNACKER JL, FORTE LR, AND BURNS TW. Impaired release of parathyroid hormone in magnesium deficiency. J Clin
Endocrinol Metab 42: 707–717, 1976.
8. ANDERSSON M, MALMENDAL A, LINSE S, IVARSSON I, FORSEN S, AND
SVENSSON LA. Structural basis for the negative allostery between
Ca2⫹- and Mg2⫹-binding in the intracellular Ca2⫹-receptor calbindin D9K. Protein Sci 6: 1139 –1147, 1997.
9. ATTIE MF, GILL JR JR, STOCK JL, SPIEGAL AM, DOWNS RW JR, LEVINE
MA, AND MARX SJ. Urinary calcium excretion in familial hypocalciuric hypercalcemia. Persistence of relative hypocalciuria after induction of hypoparathyroidism. J Clin Invest 72: 667– 676, 1983.
10. BACHMANN S, VELÁZQUEZ H, OBERMÜLLER N, REILLY RF, MOSER D, AND
ELLISON DH. Expression of the thiazide-sensitive Na-Cl cotransporter by rabbit distal convoluted tubule cells. J Clin Invest 96:
2510 –2514, 1995.
11. BACSKAI BJ AND FRIEDMAN PA. Activation of latent Ca2⫹ channels in
renal epithelial cells by parathyroid hormone. Nature 347: 388 –391,
1990.
12. BAI M, JANICIC N, TRIVEDI S, QUINN SJ, COLE DEC, BROWN EM, AND
HENDY GN. Markedly reduced activity of mutant calcium-sensing
receptor with an inserted alu element from a kindred with familial
hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism. J Clin Invest 99: 1917–1925, 1997.
13. BAI M, QUINN S, TRIVEDI S, KIFOR O, PEARCE SHS, POLLAK MR,
KRAPCHO K, HEBERT SC, AND BROWN EM. Expression and character-
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
ization of inactivating and activating mutations in the human Cao2⫹sensing receptor. J Biol Chem 271: 19537–19545, 1996.
BAI M, TRIVEDI S, AND BROWN EM. Dimerization of the extracellular
calcium-sensing receptor (CaR) on the cell surface of CaR-transfected HEK293 cells. J Biol Chem 273: 23605–23610, 1998.
BAI M, TRIVEDI S, KIFOR O, QUINN SJ, AND BROWN EM. Intermolecular
interactions between dimeric calcium-sensing receptor monomers
are important for its normal function. Proc Natl Acad Sci USA 96:
2834 –2839, 1999.
BAILLY C AND AMIEL C. Effect of glucagon on magnesium renal
reabsorption in the rat. Pflügers Arch 392: 360 –365, 1982.
BAILLY C, IMBERT-TEBOUL M, CHABARDÉS D, HUS-CITHAREL A, MONTÉGUT M, CLIQUE A, AND MOREL F. The distal nephron of rat kidney:
a target site for glucagon. Proc Natl Acad Sci USA 77: 3422–3424,
1980.
BAILLY C, IMBERT-TEBOUL M, ROINEL N, AND AMIEL C. Isoproterenol
increases Ca, Mg, and NaCl reabsorption in mouse thick ascending
limb. Am J Physiol Renal Fluid Electrolyte Physiol 258: F1224 –
F1231, 1990.
BAILLY C, ROINEL N, AND AMIEL C. Stimulation by glucagon and PTH
of Ca and Mg reabsorption in the superficial distal tubule of the rat
kidney. Pflügers Arch 403: 28 –34, 1985.
BAPTY BW, DAI LJ, RITCHIE G, CANAFF L, HENDY GN, AND QUAMME GA.
Activation of Mg2⫹/Ca2⫹-sensing inhibits hormone-stimulated
Mg2⫹ uptake in mouse distal convoluted tubule cells. Am J Physiol
Renal Physiol 275: F353–F360, 1998.
BAPTY BW, DAI LJ, RITCHIE G, JIRIK F, CANAFF L, HENDY GN, AND
QUAMME GA. Extracellular Mg2⫹ and Ca2⫹ sensing in mouse distal
convoluted tubule cells. Kidney Int 53: 583–592, 1998.
BARAJAS L, POWERS K, AND WANG P. Innervation of the renal cortical
tubules: a quantitative study. Am J Physiol Renal Fluid Electrolyte
Physiol 247: F50 –F60, 1984.
BARTON CH, VAZIRI ND, MARTIN DC, CHOI S, AND ALIKHANI S. Hypomagnesemia and renal wasting in renal transplant patients receiving cyclosporine. Am J Med 83: 693– 699, 1987.
BARTTER FC, PROVOE P, GILL JR JR, AND MACCARDLE RC. Hyperplasia
of the juxtaglomerular complex with hyperaldosteronism and hypokalemic alkalosis. A new syndrome. Am J Med 33: 811– 828, 1962.
BELL DR, WOODS RL, AND LEVI JA. cis-Diamminedichloroplatinuminduced hypomagnesemia and renal magnesium wasting. Eur J
Cancer Clin Oncol 21: 287–290, 1985.
BETTINELLI A. Use of calcium excretion values to distinguish two
forms of primary renal tubular hypokalemic alkalosis: Bartter and
Gitelman syndromes. J Pediatr 120: 38 – 43, 1992.
BETTINELLI A, BASILICO E, METTA MG, BORELLA P, JAEGER P, AND
BIANCHETTI MG. Magnesium supplementation in Gitelman syndrome. Pediatr Nephrol 13: 311–314, 1999.
BETTINELLI A, BIANCHETTI MG, BORELLA P, VOLPINI E, METTA MG,
BASILICO E, SELICORNI A, BARGELLINI A, AND GRASSI MR. Genetic
heterogeneity in tubular hypomagnesemia-hypokalemia with hypocalciuria (Gitelman’s syndrome). Kidney Int 47: 547–551, 1995.
BETTINELLI A, BIANCHETTI MG, GIRARDIN E, CARINGELLA A, CECCONI M,
APPIANI AC, PAVANELLO L, GASTALDI R, ISIMBALDI C, AND LAMA G. Use
of calcium excretion values to distinguish two forms of primary
renal tubular hypokalemic alkalosis: Bartter and Gitelman syndromes. J Pediatr 120: 38 – 43, 1992.
BETTINELLI A, VEZZOLI G, COLUSSI G, BIANCHETTI MG, SERENI F, AND
CASARI G. Genotype-phenotype correlations in normotensive patients with primary renal tubular hypokalemic alkalosis. J Nephrol
11: 61–70, 1987.
BINDELS RJM, DEMPSTER JA, RAMAKERS PLM, WILLEMS PHGM, AND
VAN OS CH. Effect of protein kinase C activation and down-regulation on active calcium transport. Kidney Int 43: 295–300, 1993.
BINDELS RJM, HARTOG A, TIMMERMANS J, AND VAN OS CH. Active Ca2⫹
transport in primary cultures of rabbit kidney CCD: stimulation by
1,25-dihydroxyvitamin D3 and PTH. Am J Physiol Renal Fluid
Electrolyte Physiol 261: F799 –F807, 1991.
BINDELS RJM, TIMMERMANS JAH, HARTOG A, COERS W, AND VAN OS CH.
Calbindin-D9K and parvalbumin are exclusively located along basolateral membranes in rat distal nephron. J Am Soc Nephrol 2:
1122–1129, 1991.
BLUMBERG D, BONETTI A, JACOMELLA V, CAPILLO S, TRUTTMANN AC,
LUTHY CM, COLOMBO JP, AND BIANCHETTI MG. Free circulating mag-
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
We acknowledge Lucie Canaff and Dr. Geoffrey Hendy for
their collaboration on the Ca2⫹-sensing receptor studies. We
thank Dr. Peter Friedman for the MDCT cells. We appreciate
Drs. Michele Gagnan-Brunette and Iwan C. Meij for fruitful
discussions and critical reading of parts of this manuscript.
This work was supported by Medical Research Council of
Canada Research Grant MT-5793 and by grants from the Kidney
Foundation of Canada (to G. A. Quamme), the National Sciences
and Engineering Research Council, and the Dairy Farmers of
Canada (to D. E. C. Cole).
Address for reprint requests and other correspondence:
G. A. Quamme, Dept. of Medicine, University Hospital, Koerner
Pavilion, 2211 Wesbrook Mall, Vancouver, BC, Canada V6T 1Z3
(E-mail: [email protected]).
14.
77
78
35.
36.
37.
38.
39.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
nesium and renal magnesium handling during acute metabolic
acidosis in humans. Am J Nephrol 18: 233–236, 1998.
BONVALET JP, PRADELLES P, AND FARMAN N. Segmental synthesis and
actions of prostaglandins along the nephron. Am J Physiol Renal
Fluid Electrolyte Physiol 253: F377–F387, 1987.
BORKE JL, CARIDE A, VERMA AK, PENNISTON JT, AND KUMAR R. Plasma
membrane calcium pump and 28-kDa calcium binding protein in
cells of rat kidney distal tubules. Am J Physiol Renal Fluid Electrolyte Physiol 257: F842–F849, 1989.
BOUBY N, TRINH-TRANG-TAN MM, AND BANKIR L. Stimulation of tubular reabsorption of magnesium and calcium by antidiuretic hormone in conscious rats: study in Brattleboro rats with hereditary
hypothalamic diabetes insipidus. Pflügers Arch 402: 458 – 464, 1984.
BOUHTIAUY I, LAJEUNESSE D, AND BRUNETTE MG. The mechanisms of
parathyroid hormone action on calcium reabsorption by the distal
tubule. Endocrinology 128: 251–258, 1991.
BOUHTIAUY I, LAJEUNESSE D, AND BRUNETTE MG. Effect of vitamin D
depletion on calcium transport by the luminal and basolateral
membranes of the proximal and distal nephrons. Endocrinology
132: 115–120, 1993.
BOUHTIAUY L, LAJEUNESSE D, CHRISTAKOS S, AND BRUNETTE MG. Vitamin-D3-dependent calcium binding proteins increase calcium reabsorption by different mechanisms. I. Effect of CaBP-28K. Kidney
Int 45: 461– 468, 1994.
BRÄUNER-OSBORNE JENSEN HAA, SHEPPARD PO, O’HARA P, AND KROGSGAARD-LARSEN P. The agonist-binding domain of the calcium-sensing
receptor is located at the amino-terminal domain. J Biol Chem 274:
18382–18386, 1999.
BREYER RM, EMESON RB, TARNG JL, BREYER MD, DAVIS LS, ABROMSON
RM, AND FERRENBACH SM. Alternative splicing generates multiple
isoforms of a rabbit prostaglandin E2 receptor. J Biol Chem 269:
6163– 6169, 1994.
BROWN EM, GAMBA G, RICARDI D, LOMBARDI M, BUTTERS R, KIFOR O,
SUN A, HEDIGER MA, LYTTON J, AND HEBERT SC. Cloning and characterization of an extracellular Ca2⫹-sensing receptor from bovine
parathyroid. Nature 366: 575–580, 1993.
BROWN EM AND HEBERT SC. A cloned Ca2⫹-sensing receptor: a
mediator of direct effects of extracellular Ca2⫹ on renal function.
J Am Soc Nephrol 6: 1530 –1540, 1995.
BROWN EM, VASSILEV PM, AND HEBERT SC. Calcium ions as extracellular messengers. Cell 83: 676 – 682, 1995.
BRUNETTE MG, MAILLOUX J, AND LAJEUNESE D. Calcium transport
through the luminal membrane of the distal tubule. I. Interrelationship with sodium. Kidney Int 41: 281–288, 1992.
BRUNETTE MG, MAILLOUX J, AND LAJEUNESSE D. Calcium transport by
the luminal membrane of distal tubule. II. Effect of pH, electrical
potential and calcium channel inhibitors. Kidney Int 41: 289 –296,
1992.
BRUNETTE MG, VIGNEAULT N, AND CARRIÉRE S. Magnesium handing by
the papilla of the young rat. Pflügers Arch 373: 229 –235, 1978.
BRYANT DT AND ANDREWS P. Investigation of the binding of Ca2⫹,
Mg2⫹, Mn2⫹, and K⫹ to the vitamin D-dependent Ca2⫹-binding
protein from pig duodenum. Biochem J 219: 287–292, 1984.
BUNDY JT, CONNITO D, MAHONEY MD, AND PONTIER PJ. Treatment of
idiopathic renal magnesium wasting with amiloride. Am J Nephrol
15: 75–77, 1995.
BURNATOWSKA MA, HARRIS CA, SUTTON RAL, AND SEELY JF. Effects of
vitamin D on renal handling of calcium, magnesium, and phosphate
in the hamster. Kidney Int 27: 864 – 870, 1985.
BUTLEN D, VADROT S, ROSEAU S, AND MOREL F. Insulin receptors along
the rat nephron: [125I]insulin binding in microdissected glomeruli
and tubules. Pflügers Arch 412: 604 – 612, 1988.
CHABARDÉS D, IMBERT-TEBOUL M, GAGNON-BURNETTE M, AND MOREL F.
Different hormonal target sites along the mouse and rabbit
nephrons. In: Biochemical Nephrology, edited by Guder WG and
Schmidt U. Bern, Germany: Huber, 1978, p. 447– 454.
CHALLA A, PAPAEFSTATHIOU I, LAPATSANIS D, AND TSOLAS O. Primary
idiopathic hypomagnesemia in two female siblings. Acta Paediatr
84: 1075–1078, 1995.
CHEN CJ, ANAST CS, POSILLICO JT, AND BROWN EM. Effects of extracellular calcium and magnesium on cytosolic calcium concentration in fura-2-loaded bovine parathyroid cells. J Bone Miner Res 2:
319 –327, 1987.
Volume 81
56. CHEN XH, BEZPROZVANNY I, AND TSIEN RW. Molecular basis of proton
block of L-type Ca2⫹ channels. J Gen Physiol 108: 363–374, 1996.
57. CHEN Z, VAUGHN DA, BLAKELEY P, AND FANESTIL DD. Adrenocortical
steroids increase renal thiazide diuretic receptor density and response. J Am Soc Nephrol 5: 1361–1368, 1994.
58. CHERY M, BIANCALANA V, PHILIPPE C, MALPUECH G, CARLA H, GILGENKRANTZ S, MANDEL JL, AND HANAUER A. Hypomagnesemia with secondary hypocalcemia in a female with balanced X; 9 translocation:
mapping of the Xp22 chromosome breakpoint. Hum Genet 93:
587–591, 1994.
59. CLEMENS TL, MCGLADE SA, GARRETT KP, CRAVISO GL, AND HENDY GN.
Extracellular calcium modulates vitamin D-dependent calbindinD28K gene expression in chick kidney cells. Endocrinology 124:
1582–1584, 1989.
60. COBURN JW AND MASSRY SG. Changes in serum and urinary calcium
during phosphate depletion: studies on mechanism. J Clin Invest
49: 1073–1087, 1970.
61. COLEMAN RA, SMITH WL, AND NARUMIYA S. VIII International Union of
Pharmacology classification of prostanoid receptors: properties,
distribution, and structure of the receptors and their subtypes.
Pharmacol Rev 46: 205–229, 1994.
62. COLUSSI G, ROMBOLA G, BRUNATI C, AND DE FERRARI ME. Abnormal
reabsorption of Na⫹/Cl⫺ by the thiazide-inhibitable transporter of
the distal convoluted tubule in Gitelman’s syndrome. Am J Nephrol
17: 103–111, 1997.
63. COSTANZO LS. Comparison of calcium and sodium transport in early
and late rat distal tubules: effect of amiloride. Am J Physiol Renal
Fluid Electrolyte Physiol 246: F937–F945, 1984.
64. COSTANZO LS, SHEEHE PR, AND WEINER IM. Renal actions of vitamin
D in D-deficient rats. Am J Physiol 226: 864 – 870, 1974.
65. COSTANZO LS AND WINDHAGER EE. Effect of PTH, ADH and cAMP on
distal tubule Ca and Na reabsorption. Am J Physiol Renal Fluid
Electrolyte Physiol 239: F478 –F485, 1980.
66. CRAVISO GL, GARRETT KP, AND CLEMENS JL. 1,25-Dihydroxyvitamin
D3 induces the synthesis of vitamin D-dependent calcium-binding
protein in cultured chick kidney cells. Endocrinology 120: 894 –902,
1987.
67. DAI LJ, BAPTY B, RITCHIE G, AND QUAMME GA. Glucagon and arginine
vasopressin stimulate Mg2⫹ uptake in mouse distal convoluted
tubule cells. Am J Physiol Renal Physiol 274: F328 –F335, 1998.
68. DAI LJ, BAPTY BW, RITCHIE G, KERSTAN D, AND QUAMME GA. Insulin
stimulates Mg2⫹ uptake in mouse distal convoluted tubule cells.
Am J Physiol Renal Physiol 277: F907–F913, 1999.
69. DAI LJ, BAPTY BW, RITCHIE G, AND QUAMME GA. PGE2 stimulates
Mg2⫹ uptake in mouse distal convoluted tubule cells. Am J Physiol
Renal Physiol 275: F833–F839, 1998.
70. DAI LJ, FRIEDMAN PA, AND QUAMME GA. Cellular mechanisms of
chlorothiazide and potassium depletion on Mg2⫹ uptake in mouse
distal convoluted tubule cells. Kidney Int 51: 1008 –1017, 1997.
71. DAI LJ, FRIEDMAN PA, AND QUAMME GA. Phosphate depletion diminishes Mg2⫹ uptake in mouse distal convoluted tubule cells. Kidney
Int 51: 1710 –1718, 1997.
72. DAI LJ, FRIEDMAN PA, AND QUAMME GA. Acid-base changes alter
Mg2⫹ uptake in mouse distal convoluted tubule cells. Am J Physiol
Renal Physiol 272: F759 –F766, 1997.
75. DAI LJ AND QUAMME GA. Intracellular Mg2⫹ and magnesium depletion in isolated renal thick ascending limb cells. J Clin Invest 88:
1255–1264, 1991.
76. DAI LJ, RAYMOND L, FRIEDMAN PA, AND QUAMME GA. Mechanisms of
amiloride stimulation of Mg2⫹ uptake in immortalized mouse distal
convoluted tubule cells. Am J Physiol Renal Physiol 272: F249 –
F256, 1997.
77. DAI LJ, RITCHIE G, BAPTY B, AND QUAMME GA. Aldosterone potentiates hormone-stimulated Mg2⫹ uptake in distal convoluted tubule
cells. Am J Physiol Renal Physiol 274: F336 –F341, 1998.
78. DE FRONZO RA, COOKE CR, ANDERES R, FALOONA GR, AND DAVIS PS.
The effect of insulin on renal handling of sodium, potassium,
calcium, and phosphate in man. J Clin Invest 55: 845– 855, 1975.
79. DE FRONZO RA, GOLDBERG M, AND AGUS ZS. The effects of glucose
and insulin on renal electrolyte transport. J Clin Invest 58: 83–90,
1976.
80. DE HEIDE LJ AND BIRKENHAGER JC. Bartter’s syndrome, hypomagne-
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
40.
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
January 2001
81.
82.
83.
84.
85.
87.
88.
89.
90.
91.
92.
93.
94.
95.
96.
97.
98.
99.
100.
101.
102.
103.
saemia and chondrocalcinosis. Netherlands J Med 39: 148 –152,
1991.
DEVANE J AND RYAN MP. Evidence for a magnesium-sparing action
by amiloride diuretic renal clearance studies in rats. Br J Pharmacol 79: 891– 896, 1983.
DE WEER P. Cellular sodium-potassium transport. In: The Kidney
Physiology and Pathophysiology, edited by Seldin DW and Giebisch G. New York: Raven, 1992, p. 93–112.
DIBONA GF AND SAWIN LL. Effect of renal nerve stimulation on NaCl
and water transport in Henle’s loop of the rat. Am J Physiol Renal
Fluid Electrolyte Physiol 243: F576 –F580, 1998.
DI STEFANO A, WITTNER M, NITSCHKE R, BRAITSCH R, GREGER R, BAILLY
C, AMIEL C, ROINEL N, AND DE ROUFFIGNAC C. Effects of parathyroid
hormone and calcitonin on Na⫹, Cl⫺, K⫹, Mg2⫹ and Ca2⫹ transport
in cortical and medullary thick ascending limbs of mouse kidney.
Pflügers Arch 417: 161–167, 1990.
DOUCET A, BARLET-BAS C, SIAUME-PEREZ S, KHADOURI C, AND MARSY S.
Gluco- and mineralocorticoids control adenylate cyclase in specific
nephron segments. Am J Physiol Renal Fluid Electrolyte Physiol
258: F812–F820, 1990.
DUARTE CG. Effects of chlorothiazide and amipirorizide (MK 870)
on the renal excretion of calcium, phosphate and magnesium.
Metabolism 17: 420 – 429, 1968.
DUARTE CG. Magnesium metabolism in potassium-depleted rats.
Am J Physiol Renal Fluid Electrolyte Physiol 234: F466 –F471,
1978.
DUDIN KI AND TEEBI AS. Primary hypomagnesaemia. A case report
and literature review. Eur J Pediatr 146: 303–305, 1987.
DUNN MJ AND WALSER MR. Magnesium depletion in normal man.
Metabolism 15: 884 – 893, 1964.
EKNOYAN G, SUKI WN, AND MARTINEZ-MALDONADO M. Effect of diuretics on urinary excretion of phosphate, calcium, and magnesium in
thyroparathyroidectomized dogs. J Lab Clin Med 76: 257–266, 1970.
ELALOUF JM, CHABANE-SARI D, AND DE ROUFFIGNAC C. Additivity of
the effects of glucagon and vasopressin on renal Mg reabsorption
and urine concentration ability in the rat. Pflügers Arch 407 Suppl
11: S566 –S596, 1986.
ELALOUF JM, ROINEL N, AND DE ROUFFIGNAC C. Stimulation by human
calcitonin of electrolyte transport in distal tubules of rat kidney.
Pflügers Arch 399: 111–118, 1983.
ELALOUF JM, ROINEL N, AND DE ROUFFIGNAC C. Effects of antidiuretic
hormone on electrolyte reabsorption and secretion in distal tubules
of rat kidney. Pflügers Arch 401: 167–173, 1984.
ELLIOTT WC AND PATCHIN DS. Aminoglycoside-mediated calciuresis.
J Pharmacol Exp Ther 262: 151–156, 1992.
EL MERNISSI G, BARLET-BAS C, KHADOURI C, CHEVAL L, MARSY S, AND
DOUCET A. Short-term effect of aldosterone on vasopressin-sensitive adenylate cyclase in rat collecting tubule. Am J Physiol Renal
Fluid Electrolyte Physiol 264: F821–F826, 1993.
ESTEP H, SHAW WA, WATINGTON C, HOBE R, HOLLAND W, AND ST.
TUCKER G. Hypocalcemia due to hypomagnesemia and reversible
parathyroid hormone unresponsiveness. J Clin Endocrinol 29:
842– 848, 1969.
EVANS RA, CARTER JN, GEORGE CRP, WALLS NEWLAND RC, MCDONNELL GD, AND LAWRENCE JR. The congenital “magnesium-losing kidney.” Report of two patients. Q J Med 197: 39 –52, 1981.
FAN G, GOLDSMITH PK, COLLINS R, DUNN CK, KRAPCHO KJ, RODGERS
KV, AND SPIEGEL AM. N-linked glycosylation of the human Ca2⫹
receptor is essential for its expression at the cell surface. Endocrinology 138: 1916 –1922, 1997.
FARMAN N, PRADELLES P, AND BONVALET JP. PGE2, PGF2␣, 6-ketoPGF1␣ and TxB2 synthesis along the rabbit nephron. Am J Physiol
Renal Fluid Electrolyte Physiol 252: F53–F59, 1987.
FEHER JJ, FULLMER CS, AND WASSERMAN RH. Role of facilitated
diffusion of calcium by calbindin in intestinal calcium absorption.
Am J Physiol Cell Physiol 262: C517–C526, 1992.
FERAILLE E, MARSY S, CHEVAL L, BARLET-BAS C, KHADOURI C, FAVRE H,
AND DOUCET A. Sites of antinatriuretic action of insulin along rat
nephron. Am J Physiol Renal Fluid Electrolyte Physiol 263: F175–
F179, 1992.
FLATMAN PW. Magnesium transport across cell membranes. J
Membr Biol 80: 1–14, 1984.
FOSTER JE, HARPUR ES, AND GARLAND HO. An investigation of the
104.
105.
106.
107.
108.
109.
110.
111.
112.
113.
114.
115.
116.
117.
118.
119.
120.
121.
122.
123.
124.
125.
126.
127.
79
acute effect of gentamicin on the renal handling of electrolytes in
the rat. J Pharmacol Exp Ther 261: 38 – 43, 1992.
FREEMAN RM AND PEARSON E. Hypomagnesemia of unknown etiology. Am J Med 41: 645– 656, 1966.
FRIEDBERG CE, VAN BUREN M, IJLSMA JA, AND KOOMANS HA. Insulin
increases sodium reabsorption in diluting segment in humans:
evidence for indirect mediation through hypokalemia. Kidney Int
40: 251–256, 1991.
FRIEDLANDER G AND AMIEL C. Decreased calcium and magnesium
urinary excretion during prostaglandin synthesis inhibition in the
rat. Prostaglandins 29: 123–132, 1985.
FRIEDMAN PA, COUTERMARSH BA, KENNEDY SM, AND GESEK FA. Parathyroid hormonal stimulation of calcium transport is mediated by
dual signalling mechanisms involving protein kinase A and protein
kinase C. Endocrinology 137: 13–20, 1996.
FRIEDMAN PA AND GESEK FA. Calcium transport in renal epithelial
cells. Am J Physiol Renal Fluid Electrolyte Physiol 264: F181–
F198, 1993.
FRIEDMAN PA AND GESEK FA. Vitamin D3 accelerates PTH-dependent
calcium transport in distal convoluted tubule cells. Am J Physiol
Renal Fluid Electrolyte Physiol 265: F300 –F308, 1993.
FRIEDMAN PA AND GESEK FA. Hormone-responsive Ca2⫹ entry in
distal convoluted tubule. J Am Soc Nephrol 4: 1396 –1404, 1994.
FRIEDMAN PA AND GESEK FA. Stimulation of calcium transport by
amiloride in mouse distal convoluted tubule cells. Kidney Int 48:
1427–1434, 1995.
GARLAND HO, BIRDSEY TJ, DAVIDGE CG, MCLAUGHLIN JT, OAKES LM,
SMITH AJ, AND HARPUR ES. Effects of gentamicin, neomycin and
tobramycin on renal calcium and magnesium handling in two rat
strains. Clin Exp Pharmacol Physiol 21: 109 –115, 1994.
GESEK FA. Stimulation of ␣2-adrenergic receptors increases Na⫹K⫹-ATPase activity in distal convoluted tubules. Am J Physiol
Renal Fluid Electrolyte Physiol 265: F561–F568, 1993.
GESEK FA. ␣2-Adrenergic receptors activate phospholipase C in
renal epithelial cells. Mol Pharmacol 50: 407– 414, 1996.
GESEK FA AND FRIEDMAN PA. Mechanism of calcium transport stimulated by chlorothiazide in mouse distal convoluted tubule cells.
J Clin Invest 90: 429 – 438, 1992.
GESEK FA AND FRIEDMAN PA. On the mechanism of parathyroid
hormone stimulation of calcium uptake by mouse distal convoluted
tubule cells. J Clin Invest 90: 749 –758, 1992.
GESEK FA AND FRIEDMAN PA. Calcitonin stimulates calcium transport in distal convoluted tubule cells. Am J Physiol Renal Fluid
Electrolyte Physiol 264: F744 –F751, 1993.
GESEK FA AND FRIEDMAN PA. Sodium entry mechanisms in distal
convoluted tubule cells. Am J Physiol Renal Fluid Electrolyte
Physiol 268: F89 –F98, 1995.
GESEK FA AND WHITE KE. Molecular and functional identification of
␤-adrenergic receptors in distal convoluted tubule cells. Am J
Physiol Renal Physiol 272: F712–F720, 1997.
GEVEN WB, MONNENS LA, WILLEMS JL, BUIJS W, AND HAMEL CJ.
Isolated autosomal recessive renal magnesium loss in two sisters.
Clin Genet 32: 398 – 402, 1987.
GEVEN WB, MONNENS LA, WILLEMS HL, BUIJS WC, AND TER HAAR BG.
Renal magnesium wasting in two families with autosomal dominant inheritance. Kidney Int 31: 1140 –1144, 1987.
GIAPROS VI, ANDRONIKOU S, AND CHOLEVAS VI. Renal function in
premature infants during aminoglycoside therapy. Pediatr Nephrol
9: 163–166, 1995.
GILL JR JR AND BARTTER FC. Evidence for a prostaglandin-independent defect in chloride reabsorption in the loop of Henle as a
proximal cause of Bartter’s syndrome. Am J Med 65: 766 –772, 1978.
GITELMAN HJ, GRAHAM JB, AND WELT LG. A new familial disorder
characterized by hypokalemia and hypomagnesemia. Trans Assoc
Am Phys 79: 221–223, 1996.
GONZALEZ C AND VILLASANTA U. Life-threatening hypocalcemia and
hypomagnesemia associated with cisplatin chemotherapy. Obstet
Gynecol 59: 732–734, 1982.
GÜNTHER T. Mechanisms and regulation of Mg2⫹ efflux and Mg2⫹
influx. J Miner Electrolyte Metab 19: 259 –265, 1993.
HAIJAMAE H AND MACDOWALL IG. Distribution of divalent cations at
the cellular level during primary hypomagnesemia in infancy. Acta
Paediatr Scand 61: 591–596, 1972.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
86.
DISTAL TUBULE MAGNESIUM TRANSPORT
80
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
149. HOENDEROP JGJ, VAN DER KAMP AWCM, HARTOG A, VAN DE GRAAF
SFJ, VAN OS CH, WILLIAMS PHGM, AND BINDELS RJM. Molecular
identification of the apical Ca2⫹ channel in 1,25-dihydroxyvitamin
D3-responsive epithelia. J Biol Chem 274: 8375– 8379, 1999.
150. HOENDEROP JGJ, VAN DER KAMP AWCM, HARTOG A, VAN OS CH,
WILLIAMS PHGM, AND BINDELS RJM. The epithelial calcium channel,
EcaC, is activated by hyperpolarization and regulated by cytosolic
calcium. Biochem Biophys Res Commun 261: 488 – 492, 1999.
151. HOENDEROP JGJ, WILLEMS PHGM, AND BINDELS RJM. Towards a
comphrehensive molecular model of active calcium reabsorption.
Am J Physiol Renal Physiol 278: F352–F360, 2000.
152. HUSMANN MJ, FUCHS P, TRUTTMANN AC, LAUX-END R, MULLIS PE,
PEHEIM E, AND BIANCHETTI MG. Extracellular magnesium depletion
in pediatric patients with insulin-dependent diabetes mellitus.
Miner Electrolyte Metab 23: 121–124, 1997.
153. ITO O, KONDO Y, TAKAHASHI N, KUDO K, IGARASHI Y, IMAI Y, OMATO K,
AND ABE K. Insulin stimulates NaCl transport in isolated perfused
MTAL of Henle’s loop of rabbit kidney. Am J Physiol Renal Fluid
Electrolyte Physiol 267: F265–F270, 1994.
154. IWATA F, HANAWA Y, AND TAKASHIMA H. Chronic hypomagnesemia
and hypokalemia due to renal wasting in siblings. Acta Paediatr
Japonica 35: 252–257, 1992.
155. JACKSON BA, BRAUN-WERNESS JL, KUSANO E, AND DOUSA TP. Concentrating defect in the adrenalectomized rat. Abnormal vasopressinsensitive cyclic adenosine monophosphate metabolism in the papillary collecting duct. J Clin Invest 72: 997–1004, 1983.
156. KAISSLING B AND LOFFING J. Cell growth and cell death in renal distal
tubules, associated with diuretic traetment. Nephrol Dial Transplant 13: 1341–1343, 1998.
157. KAISSLING B AND STANTON BA. Adaptation of distal tubule and collecting duct to increased sodium delivery. I. Ultrastructure. Am J
Physiol Renal Fluid Electrolyte Physiol 255: F1256 –F1268, 1988.
158. KAMEL KS, HARVEY E, DOUEK K, PARMAR MS, AND HALPERIN ML.
Studies on the pathogenesis of hypokalemia in Gitelman’s syndrome: role of bicarbonaturia and hypomagnesemia. Am J Nephrol
18: 42– 49, 1998.
159. KANG H-S, DAI LJ, RITCHIE G, KERSTAN D, AND QUAMME GA. Aminoglycosides inhibit hormone-stimulated Mg2⫹ uptake in mouse distal
convoluted tubule cells. J Can Physiol Pharmacol 78: 595– 602,
2000.
160. KAROLYI L, ZIEGLER A, POLLAK M, FISCHBACH M, GRZESCHIK KH, KOCH
MC, AND SEYBERTH HW. Gitelman’s syndrome is genetically distinct
from other forms of Bartter’s syndrome. Pediatr Nephrol 10: 551–
554, 1996.
161. KEATING MJ, SETHI MR, BODEY GP, AND SAMAAN NA. Hypocalcemia
with hypoparathyroidism and renal tubular dysfunction associated
with aminoglycoside therapy. Cancer 39: 1410 –1414, 1977.
162. KELEPOURIS E AND AGUS ZS. Hypomagnesemia: renal magnesium
handling. Semin Nephrol 18: 58 –73, 1998.
163. KIRCHNER KA. Insulin increases loop segment chloride reabsorption
in the euglycemic rat. Am J Physiol Renal Fluid Electrolyte
Physiol 255: F1206 –F1213, 1988.
164. KOCKERLING A, REINALTER SC, AND SEYBERTH HW. Impaired response
to furosemide in hyperprostaglandin E syndrome: evidence for a
tubular defect in the loop of Henle. J Pediatr 129: 519 –528, 1996.
165. KOREN W, PELEG E, ROSENTHAL T, AND POSTNOV YV. Membrane ion
transport in Bartter’s syndrome: evidence for a new syndrome
subtype. Hypertension 30: 1338 –1341, 1997.
166. KOSTER HPG, HARTOG A, VAN OS CH, AND BINDELS RJM. CalbindinD28k facilitates cytosolic calcium transport without interfering with
calcium signalling. Cell Calcium 18: 187–196, 1995.
167. KOSTER HPG, HARTOG A, VAN OS CH, AND BINDELS RJM. Inhibition of
Na⫹ and Ca2⫹ reabsorption by P2u purinoceptors requires PKC but
not Ca2⫹ signaling. Am J Physiol Renal Fluid Electrolyte Physiol
270: F53–F60, 1996.
168. KOEPPEN BM AND STANTON BA. Sodium chloride transport: distal
nephron. In: The Kidney: Physiology and Pathophysiology (2nd
ed.), edited by Seldin DW and Giebisch G. New York: Raven, 1992,
p. 2003–2039.
169. KRISTIANSEN JH, BROCHNER MORTENSE J, AND PEDERSEN KO. Familial
hypocalciuric hypercalcemia. I. Renal handling of calcium magnesium and phosphate. Clin Endocrinol 22: 103–116, 1985.
170. KRIZ W AND BANKIR L. A standard nomenclature for structures of the
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
128. HAMM HE. The many faces of G protein signaling. J Biol Chem 273:
669 – 672, 1998.
129. HANNA S. Influence of large doses of vitamin D on magnesium
metabolism in rats. Metab Clin Exp 10: 735–743, 1961.
130. HANNA S, ALCOCK N, LAZARUS B, AND MALLAN B. Changes in gut and
urinary ciliates following low calcium and magnesium diet and
administration of vitamin D. J Lab Clin Med 61: 220 –229, 1963.
131. HARRIS CA, BURNATOWSKA MA, SEELY JF, SUTTON RAL, QUAMME GA,
AND DIRKS JH. Effects of parathyroid hormone on electrolyte transport in the hamster nephron. Am J Physiol Renal Fluid Electrolyte
Physiol 246: F745–F756, 1984.
132. HARTLE JE II, PIPIC V, SIDDHANTI SR, SPURNEY RF, AND QUARLES LD.
Differential regulation of receptor-stimulated cyclic adenosine
monophosphate production by polyvalent cations in MC3T3–E1
osteoblasts. J Bone Miner Res 11: 789 –799, 1996.
133. HEATH H III, ODELBERG S, JACKSON CF, THE BT, HAYWARD N, LARSSON
C, BUIST NRM, KRAPCHO KJ, HUNG BC, CAPUANO IV, GARRETT JE, AND
LEPPERT MF. Clustered inactivating mutations and benign polymorphisms of the calcium receptor gene in familial benign hypocalciuric hypercalcemia suggest receptor functional domains. J Clin
Endocrinol Metab 81: 1312–1317, 1996.
134. HÉBERT RL, JACOBSON HR, AND BREYER MD. PGE2 inhibits AVPinduced water flow in cortical collecting ducts by protein kinase C
activation. Am J Physiol Renal Fluid Electrolyte Physiol 259:
F318 –F325, 1990.
135. HÉBERT RL, JACOBSON HR, FREDIN D, AND BREYER MD. Evidence that
separate PGE2 receptors modulate water and sodium transport in
rabbit cortical collecting duct. Am J Physiol Renal Fluid Electrolyte Physiol 265: F643– 650, 1993.
136. HEBERT SC. Extracellular calcium-sensing receptor: implications
for calcium and magnesium handling in the kidney. Kidney Int 50:
2129 –2139, 1996.
137. HEMMINGSEN C, STAUN M, AND OLGAARD K. Effects of magnesium on
renal and intestinal calbindin-D. Miner Electrolyte Metab 20: 265–
273, 1994.
138. HENROTTE JG. Genetic factors regulating magnesium concentrations in plasma and erythrocytes. Clin Chem 32: 1997, 1986.
139. HENROTTE JG. Genetic regulation of blood and tissue magnesium
content in mammals. Magnesium 7: 306 –314, 1988.
140. HENROTTE JG, AYMARD N, ALLIX M, AND BOULU RG. Effect of pyridoxine and magnesium on stress-induced gastric ulcers in mice selected for low or high blood magnesium levels. Ann Nutr Metab 39:
285–290, 1995.
141. HENROTTE JG, FRANCK G, SANTARROMANA M, FRANCES H, MOUTON D,
AND MOTTA R. Mice selected for low and high blood magnesium
levels: a new model for stress studies. Physiol Behav 61: 653– 658,
1997.
142. HENROTTE JG, PLA M, AND DAUSSET J. HLA- and H-2-associated
variations of intra- and extracellular magnesium content. Proc Natl
Acad Sci USA 87: 1894 –1898, 1990.
143. HERRER FC. Effect of insulin on short-circuit current and sodium
transport across toad urinary bladder. Am J Physiol 209: 819 – 824,
1965.
144. HILAL G, CLAVEAU D, ZUO Q, AND BRUNETTE MG. Interaction of second
messengers on Ca2⫹ uptake by the renal distal luminal membranes
(Abstract). J Am Soc Nephrol 6: 950A, 1995.
145. HO C, CONNER DA, POLLACK MR, LADD DJ, KIFOR O, WARREN HB,
BROWN EM, SEIDMAN JG, AND SEIDMAN CE. A mouse model of human
familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism. Nature Genet 11: 389 –394, 1995.
146. HOENDEROP JGJ, DE PONT JJHH, BINDELS RJM, AND WILLEMS PGHM.
Hormone-stimulated Ca2⫹ reabsorption in rabbit kidney cortical
collecting system is cAMP-independent and involves a phorbol
ester-insensitive PKC isotype. Kidney Int 55: 225–233, 1999.
147. HOENDEROP JGJ, HARTOG A, WILLIAMS PHGM, AND BINDELS RJM.
Adenosine-stimulated Ca2⫹ reabsorption is mediated by apical A1
receptors in rabbit cortical collecting system. Am J Physiol Renal
Physiol 274: F736 –F743, 1998.
148. HOENDEROP JGJ, VAANDRAGER AB, DIJKINK L, SMOLENSKI A, GAMBARYAN S, LOHMANN SM, DE JONGE HR, WILLEMS PHGM, AND BINDELS
RJM. Atrial natriuretic peptide-stimulated Ca2⫹ reabsorption in
rabbit kidney requires membrane-targeted, cGMP-dependent protein kinase type II. Proc Natl Acad Sci USA 96: 6084 – 6089, 1999.
Volume 81
January 2001
171.
172.
173.
174.
175.
176.
178.
179.
180.
181.
182.
183.
184.
185.
186.
187.
188.
189.
190.
191.
192.
193.
194.
kidney. The Renal Commission of the International Union of Physiological Sciences (IUPS). Pflügers Acrh 411: 113–120, 1988.
KRULL F, HOYER PF, OFFNER G, AND BRODEHL J. Renal handling of
magnesium in transplanted children under cyclosporin A treatment. Eur J Pediatr 148: 148 –151, 1988.
KUMAR R. Vitamin D metabolism and mechanism of calcium transport. J Am Soc Nephrol 1: 30 – 42, 1990.
KURTZ I. Molecular pathogenesis of Bartter’s and Gitelman’s syndromes. Kidney Int 54: 1396 –1410, 1998.
LAJEUNESSE D, BOUHTIAUY I, AND BRUNETTE MG. Parathyroid hormone and hydrochlorothiazide increase calcium transport by the
luminal membrane of rabbit distal nephron segments through different pathways. Endocrinology 134: 35– 41, 1994.
LAW WM AND HEATH H III. Familial benign hypercalcemia (hypocalciuric hypercalcemia). Clinical and pathogenetic studies in 21 families. Ann Intern Med 102: 511–519, 1985.
LEE SK, QING WG, MAR W, LUYENGI L, MEHTA RG, KAWANISHI K, FONG
HHS, BEECHER CWW, KINGHORN AD, AND PEZZUTO JM. Angoline and
chelerythrine, benzophenanthridine alkaloids that do not inhibit
protein kinase C. J Biol Chem 273: 19829 –19833, 1998.
LE GRIMELLEC C, ROINEL N, AND MOREL F. Simultaneous Mg, Ca, P, K,
Na and Cl analysis in rat tubular fluid. IV. During acute Mg plasma
loading. Pflügers Arch 340: 197–210, 1973.
LE GRIMELLEC C, ROINEL N, AND MOREL F. Simultaneous Mg, Ca, P, K,
Na and Cl analysis in rat tubular fluid. III. During acute Ca plasma
loading. Pflügers Arch 346: 171–189, 1974.
LEMANN J JR, PLEUSS JA, GRAY RN, AND HOFFMANN RG. Potassium
administration reduces and potassium deprivation increases urinary calcium excretion in healthy adults. Kidney Int 39: 973–983,
1991.
LENNON EJ AND PIERING WF. A comparison of the effects of glucose
ingestion and NH4Cl acidosis on urinary calcium and magnesium
excretion in man. J Clin Invest 49: 1458 –1465, 1970.
LEVIN M AND WINAVER J. Effects of systemic alkalosis on urinary
magnesium excretion in the rat. J Miner Electrolyte Metab 15:
214 –220, 1989.
LI HY, DAI LJ, KRIEGER C, AND QUAMME GA. Intracellular Mg2⫹
concentrations following metabolic inhibition in opossum kidney
cells. Biochim Biophys Acta 1181: 307–315, 1993.
LI HY, DAI LJ, AND QUAMME GA. Effect of chemical hypoxia on
intracellular ATP and cytosolic Mg2⫹ levels. J Lab Clin Med 122:
260 –272, 1993.
LIFSHITZ F, HARRISON HC, AND HARRISON HE. Effects of vitamin D on
magnesium metabolism in rats. Endocrinology 81: 849 – 853, 1967.
LINSE S, JONSSON B, AND CHAZIN WJ. The effect of protein concentration on ion binding. Proc Natl Acad Sci USA 92: 4748 – 4752,
1995.
LIU L, KHASTGIR A, MCCAULEY JM, DUNN ST, MORRISSEY JH, CHRISTAKOS S, HUGHES MR, AND BOURDEAU JE. RT-PCR microlocalization of
mRNAs for calbindin D28K and vitamin D receptor in the murine
nephron. Am J Physiol Renal Fluid Electrolyte Physiol 270: F677–
F681, 1996.
LIU LT, NG M, IACOPINO AM, DUNN ST, HUGHES MR, AND BOURDEAU JE.
Vitamin D receptor gene expression in mammalian kidney. J Am
Soc Nephrol 5: 1251–1258, 1994.
LOFFING J, LE HIR M, AND KASSLING B. Modulation of salt transport
rate affects DNA synthesis in vivo in rat renal tubules. Kidney Int
47: 1615–1623, 1995.
LOFFING J, LOFFING-CUENI D, HEGYI I, KAPLAN MR, HEBERT SC, LE HIR
M, AND KAISSLING B. Thiazide treatment of rats provokes apoptosis
in distal tubule cells. Kidney Int 50: 1180 –1190, 1996.
LOON NR, WILCOX CS, AND UNWIN RJ. Mechanism of impaired natriuretic response to furosemide during prolonged therapy. Kidney
Int 36: 682– 689, 1989.
LYMAN NW, HEMALATHA C, VISCUSO RL, AND JACOBS MG. Cisplatininduced hypocalcemia and hypomagnesemia. Arch Int Med 140:
1513–1514, 1980.
LYTTON J, LEE SL, VAN BAAL J, BINDELS RJ, KILAV R, NAVEH-MANY T,
AND SILVER J. The kidney sodium-calcium exchanger. Ann NY Acad
Sci 779: 58 –72, 1996.
MAGIL AB, BALLON HS, AND CAMERON EC. Acute interstitial nephritis
associated with thiazide diuretics. Am J Med 69:939 –943, 1980.
MAGIL AB, MAVICHAK V, WONG NL, QUAMME GA, DIRKS JH, AND SUTTON
195.
196.
197.
198.
199.
200.
201.
202.
203.
204.
205.
206.
207.
208.
209.
210.
211.
212.
213.
214.
215.
81
RAL. Long-term morphological and biochemical observations in
cisplatin-induced hypomagnesemia in rats. Nephron 43: 223–230,
1986.
MANDON B, SIGA E, CHABARDÉS D, FIRSOV D, ROINEL N, AND DE
ROUFFIGNAC C. Insulin stimulates Na⫹, Cl⫺, Ca2⫹, and Mg2⫹ transports in TAL of mouse nephron: cross-potentiation with ADH. Am J
Physiol Renal Fluid Electrolyte Physiol 265: F361–F369, 1993.
MANDON BE, SIGA E, ROINEL N, AND DE ROUFFIGNAC C. Ca2⫹, Mg2⫹
and K⫹ transport in the cortical and medullary thick ascending
limb of the rat nephron: influence of transepithelial voltage.
Pflügers Arch 424: 558 –560, 1993.
MANILLIER C, FARMAN N, BONJOUR JP, AND BONVALET JP. 1,25(OH)2D3
binding along the rat nephron: autoradiographic study in isolated
tubular segments. Am J Physiol Renal Fluid Electrolyte Physiol
248: F296 –F307, 1985.
MANZ F, SCHARER K, JANKA P, AND LOMBECK J. Renal magnesium
wasting, incomplete tubular acidosis, hypercalciuria and nephrocalcinosis in siblings. Eur J Pediatr 128: 67–79, 1978.
MARKMANN M, ROTHMAN R, REICHMAN B, HAKES T, LEWIS JL JR, RUBIN
S, JONES W, ALMADRONES L, AND HOSKINS W. Persistent hypomagnesemia following cisplatin chemotherapy in patients with ovarian
cancer. J Cancer Res Clin Oncol 117: 89 –90, 1991.
MARTIN HE AND JONES R. The effect of NH4Cl and NaHCO3 on the
urinary excretion of Mg, Ca, and phosphate. Am Heart J 62: 206 –
210, 1961.
MARX SJ, ATTIE MF, LEVINE MA, SPIEGEL AM, DOWNS RW JR, AND
LASKER D. The hypocalciuric or benign variant of familial hypercalcemia: clinical and biochemical features in fifteen kindreds. Medicine 60: 235–242, 1981.
MASSRY SG AND COBURN JW. The hormonal and non-hormonal control of renal excretion of calcium and magnesium. Nephron 10:
66 –112, 1973.
MASSRY SG, COBURN JW, CHAPMAN LW, AND KLEEMAN CR. The effect
of long term deoxycorticosterone acetate administration on the
renal excretion of calcium and magnesium. J Lab Clin Med 71:
212–219, 1968.
MASSRY SG, COBURN JW, AND KLEEMAN CR. Renal handling of magnesium in the dog. Am J Physiol 216: 1460 –1467, 1969.
MATSUMOTO PS, OHARA A, DUCHATELLE P, AND EATON DC. Tyrosine
kinase regulates epithelial sodium transport in A6 cells. Am J
Physiol Cell Physiol 264: C246 –C250, 1993.
MATSUNGA H, STANTON BA, GESEK FA, AND FRIEDMAN PA. Epithelial Ca2⫹
channels sensitive to dihydropyridines and activated by hyperpolarizing voltages. Am J Physiol Cell Physiol 267: C157–C165, 1994.
MATZKIN H, LOTAN D, AND BOICHIS H. Primary hypomagnesemia with
a probable double magnesium transport defect. Nephron 52: 83– 86,
1989.
MAVICHAK V, COPPIN CML, WONG NML, DIRKS JH, WALKER V, AND
SUTTON RA. Renal magnesium wasting and hypocalciuria in chronic
cis-platinum nephropathy in man. Clin Sci 75: 203–207, 1988.
MAVICHAK V, WONG NL, QUAMME GA, MAGIL AB, SUTTON RAL, AND
DIRKS JH. Studies on the pathogenesis of cisplatin-induced hypomagnesemia in rats. Kidney Int 28: 914 –921, 1985.
MEIJ IC, SAAR K, VAN DEN HEUVEL LP, NUERNBERG G, VOLLMER M,
HILDEBRANDT F, REIS A, MONNENS LA, AND KNOERS NV. Hereditary
isolated renal magnesium loss maps to chromosome 11q23. Am J
Hum Genet 64: 180 –188, 1999.
MEISTER B, DAGERLIND A, NICHOLAS AP, AND HÖKEFT T. Patterns of
messenger RNA expression for adrenergic receptor subtypes in the
rat kidney. J Pharmacol Exp Ther 268: 1605–1611, 1994.
MILAZZO SC, AHERN MJ, CLELAND LG, AND HENDERSON DR. Calcium
pyrophosphate dihydrate deposition disease and familial hypomagnesemia. J Rheumatol 8: 767–771, 1981.
MILLER ER, ULLREY ZUTANT CL, HOEFER JA, AND LUECKE RW. Mineral
balance studies with the baby pig: effects of dietary vitamin D3
level on Ca, P, and Mg balance. J Nutr 85: 255–259, 1965.
MONKAWA T, KURIHARA I, KOBAYASHI K, HAYASHI M, AND SARUTA T.
Novel mutations in thiazide-sensitive Na-Cl cotransporter gene of
patients with Gitelman’s syndrome. J Am Soc Nephrol 11: 65–70,
2000.
MOREL F. Sites of hormone actions in the mammalian nephron.
Am J Physiol Renal Fluid Electrolyte Physiol 240: F159 –F164,
1981.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
177.
DISTAL TUBULE MAGNESIUM TRANSPORT
82
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME
238.
239.
240.
241.
242.
243.
244.
245.
246.
247.
248.
249.
250.
251.
252.
253.
254.
255.
256.
257.
258.
259.
response of male Fischer 344, Sprague-Dawley and Wistar rats to
administration of gentamicin. Toxicol Lett 53: 203–205, 1990.
PIZZONIA JH, GESEK FA, KENNEDY SM, COUTERMARSH BA, BACSKAI BJ,
AND FRIEDMAN PA. Immunomagnetic separation, primary culture
and characterization of cortical thick ascending limb plus distal
convoluted tubule cells from mouse kidney. In Vitro Cell Dev Biol
27: 409 – 416, 1991.
POINTILLART A, DENIS I, COLIN C, AND LACROIX H. Influence of exogenous porcine growth hormone on magnesium in intact pigs receiving normal magnesium intakes. Magnesium Res 7: 39 – 42, 1994.
POLLACK MR, BROWN HW, CHOU EM, HEBERT SC, MARX SJ, STEINMANN
B, LEVI T, SEIDMAN CE, AND SEIDMAN JG. Mutations in the Ca2⫹sensing receptor gene cause familial hypocalciuric hypercalcemia
and neonatal severe hyperparathyroidism. Cell 75: 1297–1303, 1993.
POLLACK MR, BROWN EM, ESTEP HL, MCLAINE PN, KIFOR O, PARK J,
HEBERT SC, SEIDMAN CE, AND SEIDMAN JG. Autosomal dominant
hypocalcaemia caused by a Ca2⫹-sensing receptor gene mutation.
Nature Genet 8: 303–307, 1994.
POLLACK CHOU HW, MARX SJ, STEINMANN B, COLE DEC, BRANDI ML,
PAPAPOULOS SE, MENKO FH, HENDY GN, BROWN EM, SEIDMAN CE, AND
SEIDMAN JG. Familial hypocalciuric hypercalcemia and neonatal
severe hyperparathyroidism. Effect of mutant gene dosage on phenotype. J Clin Invest 93: 1108 –1112, 1994.
POUJEOL P, TOUVAY C, ROINEL N, AND DE ROUFFIGNAC C. Stimulation
of renal magnesium reabsorption by calcitonin in the rat. Am J
Physiol Renal Fluid Electrolyte Physiol 239: F524 –F532, 1980.
PRAGA M, VARA J, GONZÁLEZ-PARRA E, ANDRÉS ALAMO C, ARAQUE A,
ORTIZ A, AND RODICIO JL. Familial hypomagnesemia with hypercalciuria and nephrocalcinosis. Kidney Int 47: 1419 –1425, 1995.
PRONICKA E AND GRUSZCZYNSKA E. Familial hypomagnesemia with
secondary hypocalcemia-autosomal or X-linked inheritance? J Inherit Metab Dis 14: 397–399, 1991.
QUAMME GA. Effect of hypercalcemia on renal tubular handling of
calcium and magnesium. Can J Physiol Pharmacol 60: 1275–1280,
1980.
QUAMME GA. Effects of intraluminal sulfate on electrolyte transfers
along the perfused rat nephron. Can J Physiol Pharmacol 59: 122–130,
1981.
QUAMME GA. Effect of furosemide on calcium and magnesium
transport in the rat nephron. Am J Physiol Renal Fluid Electrolyte
Physiol 241: F340 –F347, 1981.
QUAMME GA. Control of magnesium transport in the thick ascending
limb. Am J Physiol Renal Fluid Electrolyte Physiol 256: F197–
F210, 1989.
QUAMME GA. Laboratory evaluation of magnesium status: renal
function and free intracellular magnesium concentration. Clin Lab
Med 13: 209 –223, 1993.
QUAMME GA. Renal magnesium handling: new insights in understanding old problems. Kidney Int 52: 1180 –1195, 1997.
QUAMME GA, CARNEY SL, WONG NLM, AND DIRKS JH. Effect of parathyroid hormone on renal calcium and magnesium reabsorption in
magnesium deficient rats. Pflügers Arch 386: 59 – 65, 1980.
QUAMME GA AND DAI LJ. Presence of a novel influx pathway for Mg2⫹
in MDCK cells. Am J Physiol Cell Physiol 259: C521–C525, 1990.
QUAMME GA AND DIRKS JH. Effect of intraluminal and contraluminal
magnesium on magnesium and calcium transfer in the rat nephron.
Am J Physiol Renal Fluid Electrolyte Physiol 238: F187–F198, 1980.
QUAMME GA AND DE ROUFFIGNAC C. Renal magnesium handling. In:
The Kidney: Physiology and Pathophysiology (3rd ed.), edited by
Seldin DW and Giebisch G. New York: Raven. In press.
QUAMME GA, WONG NLM, DIRKS JH, ROINEL N, DE ROUFFIGNAC C, AND
MOREL F. Magnesium handling in the dog kidney: a micropuncture
study. Pflügers Arch 377: 95–99, 1978.
QUAMME GA, WONG NLM, SUTTON RAL, AND DIRKS JH. Interrelationship of chlorothiazide and parathyroid hormone: a micropuncture
study. Am J Physiol 229: 200 –205, 1975.
QUINN SJ, KIFOR O, TRIVEDI S, DIAZ R, VASSILEV P, AND BROWN EM.
Sodium and ionic strength sensing by the calcium receptor. J Biol
Chem 273: 19579 –19586, 1999.
RAJERISON RM, MARCHETTI J, ROY C, BOCKAERT J, AND JARD S. The
vasopressin-sensitive adenylate cyclase of the rat kidney. Effect of
adrenalectomy and corticosteroids on hormonal receptor-enzyme
coupling. J Biol Chem 249: 6390 – 6400, 1974.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
216. MOREL F AND DOUCET A. Functional segmentation of the nephron.
In: The Kidney: Physiology and Pathophysiology (2nd ed.), edited
by Seldin DW and Giebisch G. New York: Raven, 1992, p. 1049 –1086.
217. MOREL F, IMBERT-TEBOUL M, AND CHABARDÉS D. Receptors to vasopressin and other hormones in the mammalian kidney. Kidney Int
31: 512–520, 1987.
218. MORRIS AJ AND MALBON CC. Physiological regulation of G proteinlinked signaling. Physiol Rev 79: 1373–1430, 1999.
219. MORTENSEN L, HYLDSTRAP L, AND CHARLES P. Effect of vitamin D treatment in hypoparathyroid patients: a study on calcium, phosphate and
magnesium homeostasis. Eur J Endocrinol 136: 25–35, 1997.
220. MURDOCH DC, FORREST G, DAVIES DL, AND MCINNES GT. A comparison of the potassium and magnesium-sparing properties of amiloride and spironolactone in diuretic-treated normal subjects. Br J
Clin Pharmacol 35: 373–378, 1993.
221. NAKAMURA R, EMMANOUEL DS, AND KATZ AI. Insulin binding sites in
various segments of the rabbit nephron. J Clin Invest 72: 388 –392,
1983.
222. NEMETH EF AND SCARPA A. Rapid mobilization of cellular Ca2⫹ in
bovine parathyroid cells by external divalent cations. Evidence for
a cell surface calcium receptor. J Biol Chem 262: 5188 –5196, 1987.
223. NICHOLSON JC, JONES CL, POWELL HR, WALKER RG, AND MCCREDIE DA.
Familial hypomagnesemia-hypercalciuria leading to end-stage renal failure. Pediatr Nephrol 9: 74 –76, 1995.
224. NOLAND TD, CARTER CE, JACOBSON HR, AND BREYER MD. PGE2 regulates cAMP production in cultured rabbit CCD cells: evidence for
dual inhibitory mechanisms. Am J Physiol Cell Physiol 263:
C1208 –C1215, 1992.
225. NORDIO S, DONATH A, MACAGNO F, AND GATTI R. Chronic hypomagnesemia with magnesium-dependent hypocalcemia. II. A study of
the relationship between magnesium, calcium and strontium. Acta
Paediatr Scand 60: 449 – 455, 1971.
226. OBERMÜLLER N, BERNSTEIN P, VELÁZQUEZ H, REILLY RF, MOSER D,
ELLISON DH, AND BACHMANN S. Expression of the thiazide-sensitive
Na-Cl cotransporter in rat and human kidney. Am J Physiol Renal
Fluid Electrolyte Physiol 269: F900 –F910, 1995.
227. OKAZAKI R, CHIKATSU N, NAKATSU M, TAKEUCHI Y, AJIMA M, MIKI J,
FUJITA T, ARAI M, TOTSUKA Y, TANAKA K, AND FUKUMOTO S. A novel
activating mutation in calcium-sensing receptor gene associated
with a family of autosomal dominant hypocalcemia. J Clin Endocrinol Metab 84: 363–366, 1999.
228. OKUSA MD, VELÁZQUEZ H, ELLISON DH, AND WRIGHT FS. Luminal
calcium regulates potassium transport by the renal distal tubule.
Am J Physiol Renal Fluid Electrolyte Physiol 258: F423– 428, 1990.
229. PACE AJ, GAMA L, AND BREITWIESER GE. Dimerization of the calciumsensing receptor occurs within the extracellular domain and is
eliminated by Cys3 Ser mutations at Cys101 and Cys236%. J Biol
Chem 274: 11629 –11634, 1999.
230. PARSONS PP, GARLAND HO, AND HARPUR ES. Effect of gentamicin on
urinary recoveries of 45Ca from distal tubular microperfusions in
the anaesthetized rat (Abstract). J Physiol (Lond) 483: 168p, 1995.
231. PARSONS PP, GARLAND HO, HARPUR ES, AND OLD S. Acute gentamicininduced hypercalciuria and hypermagnesiuria in the rat: dose-response relationship and role of renal tubular injury. Br J Pharmacol 122: 570 –576, 1997.
232. PASSER J. Incomplete distal renal tubular acidosis in hypomagnesemiadependent hypocalcemia. Arch Intern Med 136: 462– 466, 1976.
233. PAUNIER L, RADDE IC, KOOH SW, AND CONEN PE. Primary hypomagnesemia with secondary hypocalcemia in an infant. Pediatrics 41:
385– 402, 1968.
234. PEARCE SHS, WILLIAMSON C, KIFOR O, BAI M, COULTHARD MG, DAVIES
M, LEWIS-BARNED N, MCCREDIE D, POWELL H, AND BROWN EM. A
familial syndrome of hypocalcemia with hypercalciuria due to mutations in the calcium-sensing receptor. N Engl J Med 335: 1115–
1122, 1996.
235. PERAINO RA, SUKI WN, AND STINEBAUGH BJ. Renal excretion of calcium
and magnesium during correction of metabolic acidosis by bicarbonate infusion in the dog. J Miner Electrolyte Metab 3: 87–93, 1980.
236. PETERS N, BETTINELLI A, SPICHER I, BASILICO E, METTA MG, AND
BIANCHETTI MG. Renal tubular function in children and adolescents
with Gitelman’s syndrome, the hypocalciuric variant of Bartter’s
syndrome. Nephrol Dialysis Transplant 10: 1313–1319, 1995.
237. PHIPPS DJ, SPENCER AJ, AND HARPUR ES. Comparison of the renal
Volume 81
January 2001
DISTAL TUBULE MAGNESIUM TRANSPORT
284.
285.
286.
287.
288.
289.
290.
291.
292.
293.
294.
295.
296.
297.
298.
299.
300.
301.
302.
303.
304.
305.
sodium and potassium transport. In: The Kidney Physiology and
Pathophysiology, edited by Seldin DW and Giebisch G. New York:
Raven, 1992, p. 1373–1409.
ROTH J, BROWN D, NORMAN AW, AND ORC L. Localization of the vitamin
D-dependent calcium-binding protein in mammalian kidney. Am J
Physiol Renal Fluid Electrolyte Physiol 243: F243–F252, 1982.
ROUFFIGNAC DE C. Multihormonal regulation of nephron epithelia:
achieved through combinational mode? Am J Physiol Regulatory
Integrative Comp Physiol 269: R739 –R748, 1995.
ROUFFIGNAC DE C, CORMAN B, AND ROINEL N. Stimulation by antidiuretic
hormone of electrolyte tubular reabsorption in rat kidney. Am J
Physiol Renal Fluid Electrolyte Physiol 244: F156 –F164, 1983.
ROUFFIGNAC DE C, ELALOUF JM, ROINEL N, BAILLY C, AND AMIEL C.
Similarity of the effects of antidiuretic hormone, parathyroid hormone, calcitonin and glucagon on rat kidney. In: Nephrology, edited by Robinson RR. Berlin: Springer, 1984, p. 340 –357.
ROUFFIGNAC DE C, MOREL F, MOSS N, AND ROINEL N. Micropuncture
study of water and electrolyte movements along the loop of Henle
in Psammomas with special reference to magnesium, calcium, and
phosphate. Pflügers Arch 344: 309 –326, 1973.
ROUFFIGNAC DE C AND QUAMME GA. Renal magnesium handling and
its hormonal control. Physiol Rev 74: 305–322, 1994.
RUDIN A, AURELL M, AND WILSKE J. Low urinary calcium excretion in
Bartter’s syndrome. Scand J Urol Nephrol 22: 35–39, 1988.
SAKAIRI Y, JACOBSON HR, NOLAND TD, AND BREYER MD. Luminal
prostaglandin E2 receptors regulate salt and water transport in
rabbit cortical collecting duct. Am J Physiol Renal Fluid Electrolyte Physiol 269: F257–F265, 1995.
SANDS JM, NARUSE M, BAUM M, JO I, HEBERT SC, BROWN EM, AND
HARRIS HW. Apical extracellular calcium/polyvalent cation-sensing
receptor regulating vasopressin-elicited water permeability in rat
kidney inner medullary collecting duct. J Clin Invest 99: 1399 –
1405, 1997.
SARIBAN-SOHRABY S AND FISHER RS. Guanine nucleotide-dependent
carboxymethylation: a pathway for aldosterone modulation of apical Na⫹ permeability in epithelia. Kidney Int 48: 965–969, 1995.
SCHILSKY RL AND ANDERSON T. Hypomagnesemia and renal magnesium wasting in patients receiving cisplatin. Ann Intern Med 90:
929 –931, 1979.
SCHNEIDER EG, STRANDHOY JW, WILLIS LA, AND KNOX FG. Relationship between proximal sodium reabsorption and excretion of calcium, magnesium, and phosphate. Kidney Int 4: 369 –376, 1973.
SCHULTHEIS PJ, LORENZ JN, MENETON P, NIEMAN RIDDLE TM, FLAGELLA
M, DUFFY JJ, DOETSCHMAN T, MILLER ML, AND SHULL GE. Phenotype
resembling Gitelman’s syndrome in mice lacking the apical Na⫹Cl⫺ cotransporter of the distal convoluted tubule. J Biol Chem 273:
29150 –29155, 1998.
SCOBLE JE, SCREATON GR, AND HAVARD CW. Renal magnesium wasting
in Bartter’s syndrome. Nephrol Dialysis Transplant 5: 388 –390, 1990.
SHAFIK IM AND QUAMME GA. Early adaptation of renal magnesium
reabsorption in response to magnesium restriction. Am J Physiol
Renal Fluid Electrolyte Physiol 257: F974 –F977, 1989.
SHAH GM AND KIRSCHENBAUM MA. Renal magnesium wasting associated
with therapeutic agents. Miner Electrolyte Metab 17:58 – 64, 1991.
SHALEV H, PHILLIP M, GALIL A, CARMI R, AND LANDAU D. Clinical
presentation and outcome in primary familial hypomagnesaemia.
Arch Dis Child 78: 127–130, 1998.
SHAPIRO JR, YONG CKK, AND QUAMME GA. Influence of chronic
dietary acid on renal tubular handling of magnesium. Pflügers Arch
407: 492– 498, 1987.
SHILS ME. Experimental human magnesium depletion. Medicine 48:
61– 85, 1989.
SHIMIZU T, NAKAMURA M, YOSHITOMI K, AND IMAI M. Interaction of
trichlorothiazide or amiloride with PTH in stimulating calcium
absorption in the rabbit connecting tubule. Am J Physiol Renal
Fluid Electrolyte Physiol 261: F36 –F43, 1991.
SIMON DB, BINDRA RS, MANSFIELD TA, NELSON-WILLIAMS C, MENDONCA
E, STONE R, SCHURMAN S, NAYIR A, ALPAY H, BAKKALOGLU A, RODRIGUEZ-SORIANO J, MORALES JM, SANJAD SA, TAYLOR CM, PILZ D, BREM A,
TRACHTMAN H, GRISWOLD W, RICHARD GA, AND LIFTON RP. Mutations
in the chloride channel gene, CLCNKB, cause Bartter’s syndrome
type III. Nature Genet 17: 171–178, 1997.
SIMON DB, KARET FE, HAMDAN JM, DI PIETRO A, SANJAD SA, AND
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
260. RAMOS EL, BARRI YM, KUBILIS P, PETERSON JC, PFAFF WW, HOWARD RJ,
PARRIS CJ, PATTON PR, AND KARLIX JL. Hypomagnesemia in renal transplant patients: improvement over time and association with hypertension and cyclosporine levels. Clin Transplant 9: 185–189, 1995.
261. RUAT M, SNOWMAN AM, HESTER LD, AND SNYDER SH. Cloned and expressed rat Ca2⫹-sensing receptor: differential cooperative responses
to calcium and magnesium. J Biol Chem 271: 5972–5975, 1996.
262. RECORD RD, JOHNSON M, LEE S, AND BLAZER-YOST BL. Aldosterone
and insulin stimulate amiloride-sensitive sodium transport in A6
cells by additive mechanisms. Am J Physiol Cell Physiol 271:
C1079 –C1084, 1996.
263. REILLY RF AND ELLISON DH. Mammalian distal tubule: physiology,
pathophysiology, and molecular anatomy. Physiol Rev 80: 277–313,
2000.
264. REILLY RF, SHUGRUE C, PHILIPSON K, AND BIEMESDERFER D. Immunolocalization of the Na⫹/Ca2⫹ exchanger in rabbit kidney. Am J
Physiol Renal Fluid Electrolyte Physiol 265: F327–F332, 1993.
265. RICCARDI D. Cell surface, Ca2⫹ (cation)-sensing receptor(s): one or
many? Cell Calcium 26: 77– 83, 1999.
266. RICCARDI D, HALL AE, CHATTOPADHYAY N, XU JZ, BROWN EM, AND
HEBERT SC. Localization of the extracellular Ca2⫹/polyvalent cation-sensing protein in rat kidney. Am J Physiol Renal Physiol 274:
F611–F622, 1998.
267. RICCARDI D, LEE WS, GAMBA G, BROWN EM, AND HEBERT SC. Cloning
and functional expression of a rat kidney extracellular calcium/
polyvalent cation-sensing receptor. Proc Natl Acad Sci USA 92:
131–135, 1995.
268. RICCARDI D, LEE WS, LEE K, SEGRE GV, BROWN EM, AND HEBERT SC.
Localization of the extracellular Ca2⫹-sensing receptor and PTH/
PTHrP receptor in rat kidney. Am J Physiol Renal Fluid Electrolyte
Physiol 271: F951–F956, 1996.
269. RICHARD O AND FREYCON MT. Congenital tubulopathy with magnesium loss. Pediatrie 47: 557–563, 1992.
270. RICHARDSON JA AND WELT LG. Hypomagnesemia of vitamin D administration. Proc Soc Exp Med 118: 512–514, 1965.
271. RITCHIE G, BAPTY BW, JIRIK FR, AND QUAMME GA. Differentially
expressed genes involved in regulation of epithelial Mg2⫹ transport
identified by differential display (Abstract). J Am Soc Nephrol 7:
1806A, 1996.
272. RITCHIE G, BAPTY BW, JIRIK FR, AND QUAMME GA. Differentially
expressed genes involved in regulation of epithelial Mg2⫹ transport
(Abstract). J Am Soc Nephrol 8: 566A, 1997.
273. ROB PM, LEBEAU AA, NOBILING R, SCHMID H, BLEY N, DICK K, WEIGELT
I, ROHWER J, GOBEL Y, SACK K, AND CLASSEN HG. Magnesium metabolism: basic aspects and implications of cyclosporin toxicity in
rats. Nephron 72: 59 – 66, 1996.
274. ROB PM, LEBEAU A, SCHMID H, SACK K, AND CLASSEN HG. Cyclosporin
induces magnesium deficiency in rats and thereby aggravates its
own nephrotoxicity: benefit of magnesium supplementation.
Transplant Proc 26: 1736 –1737, 1994.
275. RODRIGUEZ M, SOLANKI DL, AND WHANG R. Refractory potassium
repletion due to cisplatin-induced magnesium depletion. Arch Int
Med 149: 2592–2594, 1989.
276. RODRIGUEZ-COMMES J, ISALES C, KALGHATI L, GASALLA-HERRAIZ J, AND
HAYSLETT JP. Mechanism of insulin-stimulated electrogenic sodium
transport. Kidney Int 46: 666 – 674, 1994.
277. RODRIGUEZ PORTALES JA AND DELEA CS. Renal tubular reabsorption
of chloride in Bartter’s syndrome and other conditions with hypokalemia. Clin Nephrol 26: 269 –272, 1986.
278. RODRIGUEZ-SORIANO J. Bartter and related syndromes: the puzzle is
almost solved. Pediatr Nephrol 12: 315–327, 1998.
279. RODRÍGUEZ-SORIANO J AND VALLO A. Pathophysiology of the renal
acidification defect present in the syndrome of familial hypomagnesemia-hypercalciuria. Pediatr Nephrol 8: 431– 435, 1994.
280. RODRÍGUEZ-SORIANO J, VALLO A, AND GARCIA-FUENTES M. Hypomagnesemia of hereditary renal origin. Pediatr Nephrol 1: 465– 472, 1987.
281. ROKAW MD, BENOS DJ, PALEVSKY PM, CUNNINGHAM SA, WEST ME, AND
JOHNSON JP. Regulation of a sodium channel-associated G-protein
by aldosterone. J Biol Chem 271: 4491– 4496, 1996.
282. ROMAN RJ, SKELTON M, AND LECHENE C. Prostaglandin-vasopressin
interactions on the renal handling of calcium and magnesium.
J Pharmacol Exp Ther 230: 295–301, 1984.
283. ROSSIER BC AND PALMER LG. Mechanisms of aldosterone action on
83
84
306.
307.
308.
309.
311.
312.
313.
314.
315.
316.
317.
318.
319.
320.
321.
322.
323.
324.
325.
326.
LIFTON RP. Bartter’s syndrome, hypokalemic alkalosis with hypercalciuria, is caused by mutations in the Na-K-2Cl cotransporter
NKCC2. Nature Genet 13: 183–188, 1996.
SIMON DB, KARET FE, RODRIGUEZ-SORIANO J, HAMDAN JH, DI PIETRO A,
TRACHTMAN H, SANJAD SA, AND LIFTON PR. Genetic heterogeneity of
Bartter’s syndrome revealed by mutations in the K⫹ channel,
ROMK. Nature Genet 14: 152–156, 1996.
SIMON DB AND LIFTON RP. The molecular basis of inherited hypokalemic alkalosis: Bartter’s and Gitelman’s syndromes. Am J
Physiol Renal Fluid Electrolyte Physiol 271: F961–F966, 1996.
SIMON DB, LU Y, CHOATE KA, VELAZQUEZ H, AL-SABBAN E, PRAGA M,
CASARI G, BETTINELLI A, COLUSSI G, RODRIGUEZ-SORIANO J, MCCREDIE D,
MILFORD D, SANJAD S, AND LIFTON RP. Paracellin-1, a tight junction protein
required for paracellular Mg2⫹ resorption. Science 285: 103–106, 1999.
SIMON DB, NELSON-WILLIAMS C, BIA MJ, ELLISON FE, MARET MOLINAAM
I, VAARA F, IWATA CUSHNER HM, KOOLEN M, GAINZA FJ, GITELMAN HJ,
AND LIFTON RP. Gitelman’s variant of Bartter’s syndrome, inherited
hypokalemic alkalosis, is caused by mutations in the thiazidesensitive Na⫹Cl⫺ cotransporter. Nature Genet 12: 24 –30, 1996.
SKYBERG D, STRØMME JH, NESBAKKEN R, AND HARNOE K. Neonatal
hypomagnesemia with selective malabsorption of magnesium.
Scand J Clin Lab Invest 21: 355–361, 1968.
SOUPART A, UNGER J, DEBIEVE MF, AND DECAUX G. Bartter’s syndrome
with a salt reabsorption defect in the cortical part of Henle’s loop.
Am J Nephrol 8: 309 –315, 1988.
STANTON BA. Cellular actions of thiazide diuretics in the distal
tubule. J Am Soc Nephrol 1: 832– 836, 1990.
STOKES JB. Effect of prostaglandin E2 on chloride transport across the
rabbit thick ascending limb of Henle. J Clin Invest 64: 495–502, 1979.
STROMME JH, NESBAKKEN R, NORMANN T, SKJORTEN F, SKYBERG D, AND
JOHANNESSEN B. Familial hypomagnesemia. Biochemical, histological and hereditary aspects studied in two brothers. Acta Paediatr
Scand 58: 433– 444, 1969.
STROMME JH, STEEN-JOHNSEN J, HARNAES K, HOFSTAD F, AND
BRANDTZAEG P. Familial hypomagnesemia—a follow-up examination of three patients after 9 to 12 years of treatment. Pediatr Res
15: 1134 –1139, 1981.
STUMPF WE, SAR M, NARBAITZ R, REID FA, DE LUCA HF, AND TANAKA
Y. Cellular and subcellular localization of 1,25(OH)2-vitamin D3 in
rat kidney, comparison with localization of parathyroid hormone
and oestradiol. Proc Natl Acad Sci USA 77: 1149 –1153, 1980.
SUGIMOTO Y, NAMBA T, SHIGEMOTO R, NEGISHI M, ICHIKAWA A, AND
NARUMIYA S. Distinct cellular localization of mRNAs for three subtypes of prostaglandin E receptor in kidney. Am J Physiol Renal
Fluid Electrolyte Physiol 266: F823–F828, 1994.
SUH SM, TASHJIAN AH JR, MATSUO N, PARKINSON DK, AND FRASER D.
Pathogenesis of hypocalcemia in primary hypomagnesemia: normal end-organ responsiveness to parathyroid hormone, impaired
parathyroid gland function. J Clin Invest 52: 153–160, 1973.
SUKI WN, SCHWETTMANN RS, RECTOR FC JR, AND SELDIN DW. Effect of
chronic mineralocorticoid administration or calcium excretion in
the rat. Am J Physiol 215: 71–74, 1968.
SUTTON RAL, MAVICHAK V, HALABE A, AND WILKINS GE. Bartter’s syndrome: evidence suggesting a distal tubular defect in a hypocalciuric
variant of the syndrome. Miner Electrolyte Metab 18: 43–51, 1992.
SUTTON RAL, WALKER VR, HALABE A, SWENERTON K, AND COPPIN CM.
Chronic hypomagnesemia caused by cisplatin: effect of calcitriol.
J Lab Clin Med 117: 40 – 43, 1991.
SWAINSON CP, COLLS BM, AND FITZHARRIS BM. Cis-platinum and distal
renal tubule toxicity. New Zealand Med J 98: 375–378, 1985.
TAKAHASHI N, IGARASHI P, AND SMITHIES O. A mouse model of neonatal Bartter’s syndrome (Abstract). J Am Soc Nephrol 10: 44A, 1999.
TAYLOR AN, MCINTOSH JE, AND BOURDEAU JE. Immunocytochemical
localization of vitamin D-dependent calcium binding protein in
renal tubules of rabbit, rat, and chick. Kidney Int 21:765–773, 1983.
TORRALBO A, PINA E, PORTOLÉS J, AND BARRIENTOS A. Renal magnesium wasting with hypercalciuria, nephrocalcinosis and ocular disorders. Nephron 69: 472– 475, 1995.
TSUKAMOTO T, KOBAYASHI T, KAWAMOTO K, FUKASE M, AND CHIHARA K.
Possible discrimination of Gitelman’s syndrome from Bartter’s syndrome by renal clearance study: report of two cases. Am J Kidney
Dis 25: 637– 641, 1995.
Volume 81
327. TURMAN MA. Concomitant occurrence of Gitelman and Bartter syndromes in the same family? Pediatr Nephrol 12: 23–25, 1998.
328. ULMANN A, HADJ S, LACOUR B, BOURDEAU A, AND BADER CC. Renal
magnesium and phosphate wastage in a patient with hypercalciuria
and nephrocalcinosis: effect of oral phosphorus and magnesium
supplements. Nephron 40: 83– 87, 1985.
329. VAN BAAL J, DE JONG MD, FIJLSTRA FJ, WILLEMS PH, AND BINDELS RJ.
Endogenously produced prostanoids stimulate calcium reabsorption in the rabbit cortical collecting system. J Physiol (Lond) 497:
229 –239, 1996.
330. VAN BAAL J, YU A, HARTOG A, FRANSEN JA, WILLEMS PH, LYTTON J, AND
BINDELS RJ. Localization and regulation by vitamin D of calcium
transport proteins in rabbit cortical collecting system. Am J
Physiol Renal Fluid Electrolyte Physiol 271: F985–F993, 1996.
331. VAN BAAL J, HOENDEROP JGJ, GROENENDIJK M, VAN OS CH, BINDELS
RJM, AND WILLEMS PHGM. Hormone-stimulated Ca2⫹ transport in
rabbit kidney: multiple sites of inhibition by exogenous ATP. Am J
Physiol Renal Physiol 277: F899 –F906, 1999.
332. VAN OS CH. Transcellular calcium transport in intestinal and renal
epithelial cells. Biochim Biophys Acta 906: 195–222, 1987.
333. VELÁZQUEZ H, NÁRAY-FEJES-TÓTH A, SILVA T, ANDÚJAR E, REILLY RF,
DESIR GV, AND ELLISON DH. Rabbit distal convoluted tubule coexpresses NaCl cotransporter and 11␤-hydroxysteroid dehydrogenase II mRNA. Kidney Int 54: 464 – 472, 1998.
334. VON DER WEID NX, ERNI BM, MAMIE C, WAGNER HP, AND BIANCHETTI
MG. Cisplatin therapy in childhood: renal follow up 3 years or more
after treatment Swiss Pediatric Oncology Group. Nephrol Dialysis
Transplant 14: 1441–1444, 1999.
335. WALDER RY, SHALEV H, BRENNAN TM, CARMI R, ELBEDOUR K, SCOTT
DA, HANAUER A, MARK AL, PATIL S, STONE EM, AND SHEFFIELD VC.
Familial hypomagnesemia maps to chromosome 9q, not to the X
chromosome: genetic linkage mapping and analysis of a balanced
translocation breakpoint. Hum Mol Genet 6: 1491–1497, 1997.
336. WANG WH, LA M, AND HEBERT SC. Cytochrome P-450 metabolites
mediate extracellular Ca2⫹-induced inhibition of apical K⫹ channels in the TAL. Am J Physiol Cell Physiol 271: C103–C111, 1996.
337. WEINBERG JM, HARDING PG, AND HUMES HD. Alterations in renal
cortex cation homeostasis during mercuric chloride and gentamicin nephrotoxicity. Exp Mol Pathol 39: 43– 60, 1983.
338. WELCH TR. The hyperprostaglandin E syndrome: a hypercalciuric
variant of Bartter’s syndrome J. Bone Miner Res 12: 1753–1754, 1997.
339. WESTER PO. Electrolyte balance in heart failure and the role for
magnesium ions. Am J Cardiol 70: 44C– 49C, 1992.
340. WHANG R. Magnesium deficiency: pathogenesis, prevalence, and
clinical implications. Am J Med 82: 24 –29, 1987.
341. WHANG R, WHANG DD, AND RYAN MP. Refractory potassium depletion: a consequence of magnesium deficiency. Arch Intern Med 152:
40 – 45, 1992.
342. WITTNER M AND DI STEFANO A. Effects of antidiuretic hormone,
parathyroid hormone and glucagon on the cortical and medullary
thick ascending limb of Henle’s loop of the mouse nephron.
Pflügers Arch 415: 707–712, 1990.
343. WONG NL AND DIRKS JH. Cyclosporin-induced hypomagnesaemia
and renal magnesium wasting in rats. Clin Sci 75: 509 –514, 1988.
344. WONG NLM, DIRKS JH, AND QUAMME GA. Tubular maximum reabsorptive capacity for magnesium in the dog. Am J Physiol Renal
Fluid Electrolyte Physiol 244: F78 –F83, 1983.
345. WONG NLM, QUAMME GA, AND DIRKS JH. Effect of chlorothiazide on
renal calcium and magnesium handling in the hamster. Can
J Physiol Pharmacol 60: 1160 –1165, 1982.
346. WONG NLM, QUAMME GA, AND DIRKS JH. Effects of acid-base disturbances on renal handling of magnesium in the kidney. Clin Sci 70:
277–284, 1986.
347. WONG NLM, QUAMME GA, O’CALLAGHAN TJ, SUTTON RAL, AND DIRKS
JH. Renal and tubular transport in phosphate depletion: a micropuncture study. Can J Physiol Pharmacol 58: 1063–1071, 1980.
348. WU X, ACKERMANN U, AND SONNENBERG H. Potassium depletion and
salt-sensitive hypertension in Dahl rats: effects on calcium, magnesium, and phosphate excretion. Clin Exp Hypertens 17: 989–1008, 1995.
349. YANG T, HASSAN S, HUANG YG, SMART AM, BRIGGS JP, AND SCHNER2⫹
MANN JB. Expression of PTHrP, PTH/PTHrP receptor and Ca
sensing receptor along the rat nephron. Am J Physiol Renal
Physiol 272: F751–758, 1997.
Downloaded from http://physrev.physiology.org/ by 10.220.33.1 on July 4, 2017
310.
DAI, RITCHIE, KERSTAN, KANG, COLE, AND QUAMME