Homologous regulation of human platelet vasopressin
receptors does not occur in vivo
DANIEL
VITTET,
JEAN-MARIE
LAUNAY,
AND
CLAUDE
CHEVILLARD
Institut National de la Sante et de la Recherche Medicale U 300, Faculte de Pharmacie,
34060 Montpellier Cedex 2; and Formation de Recherche Associee Claude Bernard: Neurochimie
des Communications
Cellulaires, HGpital St. Louis, 75475 Paris Cedex 10, France
VITTET,
ILLARD.
DANIEL,
JEAN-MARIE
LAUNAY,
AND
CLAUDE
CHEV-
Homologous regulation of human platelet vasopressin
receptors does not occur in vivo. Am. J. Physiol. 257 (Regulatory
Integrative Comp. Physiol. 26): R1400-R1405, 1989.-Large
variations in the functional responsiveness of human platelets
to arginine vasopressin (AVP), related to maximal platelet
AVP-binding capacity, have been observed among individuals.
The effects of dehydration and overhydration on maximal
platelet AVP-binding capacity, plasma AVP, platelet-associated AVP, and AVP-induced platelet aggregation were examined in healthy human volunteers to determine whether homologous regulation of platelet AVP receptors occurs in vivo
within the physiological range of circulating AVP fluctuations.
Although significant variations of plasma AVP were observed
under both conditions, no correlation could be found in the
same individual with any change in 1) the maximal AVPbinding capacity, 2) platelet aggregatory responses to AVP, or
3) the platelet AVP fraction. Moreover, there was no relationship between the number of detectable platelet AVP receptors
and the amount of AVP associated with platelets. These data
show that homologous regulation of platelet AVP receptors by
AVP does not occur in vivo over the time investigated, at least
within the physiological range of AVP. Nonetheless, regulation
at the platelet precursor stage appears to be highly probable in
view of the relationship between plasma AVP and platelet AVP
binding capacity observed among different individuals.
plasma vasopressin; dehydration; overhydration
VASOPRESSIN (AVP) causes shape change and
aggregation of human blood platelets (6, 10). AVP-induced human platelet activation appears to be mediated
by the stimulation of specific VI receptors (29) that have
activation coupled to a G protein (27) with inhibition
of
adenylate cyclase activity (28) and with stimulation
of
phosphoinositide
turnover (23) followed by increased
concentrations of cytosolic ionized calcium (9).
Large variations in platelet functional responsiveness
to AVP have been observed among healthy donors involving the aggregatory response as well as the related
transduction processes (17, 20). We have previously reported direct relationships between maximal AVP-binding capacity on human platelet membranes, maximal
AVP-stimulated
guanosine
triphosphatase
activity,
which reflects the involvement of a G protein, and maximal AVP-induced adenylate cyclase inhibition in a population of 10 healthy human subjects (27, 28).
These variations among individuals may reflect hoARGININE
R1400
0363-6119/89
$1.50
mologous in vivo regulation
of human platelet AVP
receptors. Indeed, large and variable amounts of AVP
are associated with platelet membranes (2, 5), and evidence for a functional loss of platelet AVP responsiveness after in vitro preincubation
with high concentrations of AVP has been reported in relation to the aggregatory response (8), phosphoinositide
metabolism
(l7),
and increases in the cytosolic free calcium concentration
(17). Moreover,
in patients with renal disease, high
plasma AVP concentrations
are associated with low
receptor binding capacity (14).
However, the concentrations
of AVP measured in
pathological
states, as well as those used in vitro to
induce the desensitization
of AVP-induced platelet responses, are far higher than the normal fluctuations of
plasma AVP concentrations, which are in the picomolar
range (1). Indeed, a depressed responsiveness of human
platelets to AVP has been shown in vitro after prior
incubation with 20 nM AVP, a concentration eliciting a
small reversible aggregation (8). In contrast, nothing is
known about the in vivo regulation of platelet AVP
receptors in healthy humans within the physiological
range of plasma AVP concentrations. The present study
was designed to determine whether platelet AVP receptors are regulated in vivo by physiological variations in
plasma AVP and/or in AVP associated with platelets,
which could explain the large variations in platelet functional responsiveness to AVP, as well as in platelet
maximal
AVP-binding
capacities,
observed among
healthy individuals.
Varying concentrations
of plasma
AVP levels were obtained in normal human volunteers,
by dehydration or by drinking, and the effects on platelet
maximal AVP-binding
capacity, AVP associated with
platelets, and platelet aggregatory vasopressin responses
were measured.
MATERIALSANDMETHODS
Subjects
Volunteers who participated
in the studies ranged from
28 to 50 yr of age, and their body weight differed by no
more than t15% from ideal body weight (Metropolitan
Life Insurance Tables). Each appeared to be healthy and
had received no medication
for at least 1 wk before
sampling.
Copyright 0 1989 the American Physiological Society
HOMOLOGOUS
REGULATION
OF
PLATELET
Protocol
Series 1. In a first series of experiments six volunteers
were tested. Each subject was studied on three occasions,
and blood samples were routinely taken between 8 and 9
a.m. The first sampling at the start of the experiment
was carried out when subjects still had free access to
water and were in a control state. After the first sampling, subjects were asked to reduce their fluid intake as
much as possible for 2 days without changing their food
habits. After this dehydration period, blood was again
sampled. The mean reduction of fluid intake by the
subjects was 60% of their fluid intake under control
conditions. Subjects were then asked to overhydrate by
increasing their fluid intake as much as possible for
another 2-day period after which the last blood sample
was taken. The mean increase in fluid intake was 250%
of their fluid intake under control conditions.
On each occasion, three successive blood samples were
taken from the antecubital vein for plasma osmolality
and plasma sodium measurements, for plasma AVP and
platelet AVP determinations,
and for isolation of platelets and binding studies.
Series 2. A second set of experiments was performed
to determine if in vivo homologous regulation of platelet
vasopressin responses occurred at a postreceptor level
during the various hydration stages. Three highly responsive subjects (in terms of platelet aggregatcry responses to AVP) were dehydrated and three poorly responsive subjects were overhydrated, each for 2 days as
before. Blood was taken as previously for determination
of plasma osmolality, plasma AVP, platelet maximal
AVP-binding
capacity, and functional aggregatory response to AVP.
Plasma A VP and Platelet A VP Measurements
Processing of blood for A VP assay. Blood samples (5
ml) were collected in tubes containing chilled EDTA.
Aprotinin (100 PI/tube) was added to block any proteolytic activity during the procedure. After centrifugation
at 180 g for 20 min at room temperature, platelet-rich
plasma (PRP) was obtained and 1 ml was saved. Further
centrifugation
of the remaining sample at 2,200 g for 10
min yielded platelet-poor plasma (PPP). PRP and PPP
samples were stored at -20°C for a maximum of 2 mo
before assay. The platelet content of PRP samples was
505,000 t 24,000 platelets/pi,
(means t SE, n = Is),
whereas the platelet content of PPP samples was 53,000
+- 2,650 platelets/p& (&SE, n = 18). AVP present in PPP
was called plasma AVP; the amount of AVP associated
with platelets, which could be estimated from the difference between the AVP concentrations in PRP and PPP,
was called platelet AVP.
A VP radioimmunoassay. AVP was extracted using the
acetone-petroleum
ether method (11, 19) with slight
modifications. Briefly, thawed samples (1 ml) were mixed
with 1 ml of cold acetone. After shaking and centrifugation, the supernatants were then mixed with 3 ml of cold
petroleum ether and recentrifuged. The bottom phases
were sampled and evaporated to dryness at 37°C under
a nitrogen stream. The dry residues were resuspended in
VASOPRESSIN
RECEPTOR
R1401
900 ~1 of incubation buffer (0.01 M sodium phosphate
buffer, pH 7.3, containing 0.15 M NaCl, 1 mg/ml bovine
serum albumin, and 1 mg/ml sodium azide).
To monitor AVP recovery during the extraction procedure, 10,000 counts/min (2- C3H]phenylalanine,
8-arginine)vasopressin
(New England Nuclear, Boston, MA;
90 Ci/mmol)
were added to all samples. The extreme
recovery values in the tested samples were 87.2 and
98.6%. All AVP determinations
were then corrected for
their respective extraction output.
For AVP assay, 250 ~1 of AVP standards in buffer or
250 ~1 of reconstituted extract were incubated in triplicate with 100 ~1 of tracer (2,000-3,000 counts/min)
and
with 100 ~1 of antibody diluted in buffer. After two days
at 4”C, free and bound fractions were then separated by
a dextran charcoal method.
The tracer was (3- [ 1251]iodotyrosy12,8-arginine)vasopressin (Amersham France, Les Ulis) with a high specific
activity (1,860 Ci/mmol).
Nonspecific binding was always ~4.6%. The anti-AVP antibody (a generous gift of
Dr. A. Bailly, ORIS, Saclay, France) was used at a final
dilution of l/1.35 x 105. The cross-reactivity
of this
antibody was 7.6% for lysine vasopressin, 0.6% for arginine vasotocin, and ~0.05% for oxytocin. The sensitivity
of the assay was 0.36 pg/ml. The intra- and inter-assay
variations were, respectively, 2.5 t 0.6 and 5.7 + 1.0%
(&SE, n = 15) for PPP AVP and 3.0 t 0.8 and 5.9 t
1.0% (&SE, n = 12) for PRP AVP.
Osmolality and sodium ions. Blood samples (5 ml) were
collected in tubes containing lithium-heparin.
PPP was
prepared as described for plasma AVP measurements.
Plasma osmolality
was determined
by freezing-point
depression using an Osmomat 030 Gonotec osmometer
(Vitatron, Les Ulis, France). Plasma sodium levels were
measured using a specific IL 508 electrode (Instrumentation Laboratory, Lexington, MA).
Studies of r3H]A VP Binding on Human
Platelet Membranes
Platelet membrane preparation. Blood (40 ml) was
collected in 10% (vol/vol) acid-citrate-dextrose.
Platelets
were isolated as previously described (14). Crude membranes were prepared from the platelet pellet under
similar conditions in all experiments as in a previous
work (28) in the presence of 5 mM ethylene glycol-bis( ,&
aminoethyl ether)-N,N,N’,N’-tetraacetic
acid (EGTA).
Protein concentrations were measured according to the
method of Lowry et al. (15).
Measurement of PH]AVP
binding to platelet membranes. Binding studies were performed as previously
described (29). Briefly, in all experiments, fresh platelet
membranes were incubated with the incubation medium
and with various amounts of (2-[3H]phenylalanine,
8arginine)vasopressin
(90 Ci/mmol) belonging to the same
commercial batch for 15 min at 30°C. The reaction was
then stopped and the preparation filtered through Gelman GA-3 filters. Radioactivity
of filters was measured
by liquid scintillation
counting. Nonspecific binding was
determined in the presence of 10 UM unlabeled AVP.
R1402
HOMOLOGOUS
REGULATION
P ( 0.05
155,
P(
OF
1501
145,
140,
135,
130*
125
r
0
35
3
v
4
2
P ( 0.05
p ( 0.05
-)I
7
VASOPRESSIN
RECEPTOR
Platelet Aggregation
0.05
-II
PNa
tmM 1
PLATELET
Aggregation measurements were carried out on PRP
as previously described (14). Briefly, PRP was diluted
with PPP to give a platelet count of 300,000 platelets/
~1. The aggregometer was always adjusted so that PRP
gave 0% and PPP gave 100% light transmittance.
Aggregometry was begun as soon as possible after 60 min after
venipuncture. After a first run of an aliquot of PRP for
10 min to test spontaneous aggregation, further aliquots
prewarmed for 3 min to 37°C without stirring were
transferred to the aggregometer and run for a 1 min base
line while stirring at 900 rpm before adding AVP for
measurements. Aggregation was quantified in terms of
changes in light transmittance.
RESULTS
pOsm
0
2
P ( 0.05
4
.
pAVP
(Wm’ )
piatAVP
(pa-q
2
0
4
Bmax
( fmol
/ m g protein
As expected, all subjects showed an increase in plasma
osmolality and plasma sodium at the end of the dehydration period and a decrease in these parameters after
overhydration,
which were both significant
(Fig. 1).
When subjects were dehydrated for 48 h, mean plasma
osmolality increased from 289 t 9 to 307 t 4 mosmol/
kg, and mean plasma sodium increased from 137 t 2 to
146 t 2 mmol/l. At the end of the subsequent overhydration period, these values had fallen to a level significantly different from those measured under dehydrated
conditions but close to the control levels: 285 t 8 mosmol/kg for plasma osmolality and 134 t 2 mmol/l for
plasma sodium.
Plasma AVP varied significantly
in parallel with
plasma sodium and plasma osmolality. Specifically, mean
plasma AVP increased from 2.3 t 0.4 to 3.3 t 0.5 pg/ml
during the dehydration phase and then decreased to 2.2
t 0.4 pg/ml during overhydration.
Platelet AVP was
significantly higher than plasma AVP at the start of the
test in each individual;
mean plasma AVP in the six
subjects tested was 2.3 t 0.4 pg/ml, whereas mean platelet AVP reached 15 t 4 pg/ml. However, no significant
variations of platelet AVP were observed during the
procedure. Similarly, the maximal platelet AVP-binding
capacity remained constant in each subject tested during
the various hydration stages (Fig. 1).
Moreover, variations
in platelet responsiveness to
AVP, in terms of aggregatory response, were observed
among donors: subjects with low AVP-binding
capacity
were unresponsive or poorly responsive to AVP, whereas
higher AVP-binding
capacity was associated with full
aggregatory response to AVP. However, like platelet
AVP-binding
capacities, platelet aggregatory responses
to AVP did not change significantly after dehydration in
three highly responsive donors (Table 1) or after overhydration in three poorly responsive donors (Table 2).
DISCUSSION
2
Time
(day)
FIG. 1. Effect of dehydration
(day 2) and subsequent
overhydration
(day 4) on plasma sodium (pNa),
plasma osmolality
(pOsm),
plasma
arginine
vasopressin
(pAVP),
platelet
AVP (platAVP),
and platelet
Our results concerning the effects of dehydration and
overhydration on plasma osmolality, plasma sodium, and
membrane
AVP maximal
binding
capacity
(B,,,).
Values
represent
parameters
of 6 subjects tested, each symbol corresponding
to same
subject in all graphs. Differences
between values in different
hydration
stages were assessed by Kruskall-Wallis
and Wilcoxon
nonparametric
statistical
test.
HOMOLOGOUS
TABLE
1. Effects of dehydration
REGULATION
OF
on AVP-induced
PLATELET
VASOPRESSIN
platelet aggregatory
responses
in highly responsive
Control
Values for arginine
are denoted by initials.
TABLE
%light
Dehydration
cc
AR
FL
cc
AR
301
3.8
533
309
1.9
369
305
1.8
245
320
4.6
508
318
1.8
360
324
2.1
264
54k2
27k5
46t5
24t5
23t3
12k4
57k3
18t4
23t6
12k5
28k4
11t3
transmission
vasopressin
(AVP)-induced
platelet
Bm,x, maximal
binding
capacity.
2. Effects of overhydration
aggregation
on AVP-induced
are means
* SD of 3 determinations
platelet aggregatory
responses
from
in poorly responsive
Control
Values for AVP-induced
are denoted by initials.
platelet
%light
the same experiment.
Subjects
subjects
Overhydration
GA
JB
DV
GA
JB
DV
303
2.1
160
299
5.8
42
308
4.9
170
287
1.7
150
282
2.9
66
284
2.6
166
6t2
It1
3t1
SC
421
SC
9&4
3k2
4t1
It1
SC
SC
Subjects:
Plasma osmolality,
mosmol/kgH20
Plasma AVP, pg/ml
B max9 fmol/mg
protein
AVP-induced
platelet aggregation,
lo-” M
5 x 1O-8 M
subjects
FL
Subjects:
Plasma osmolality,
mosmol/kgHzO
Plasma AVP, pg/ml
B max9 fmol/mg
protein
AVP-induced
platelet aggregation,
1O-6 M
5 x lo-’ M
R1403
RECEPTOR
transmission
aggregation
are means
t SD of 3 determinations
plasma vasopressin are in close agreement with previous
studies of the sensitive relationship between body fluid
tonicity, thirst, and vasopressin secretion changes (1).
Although in absolute terms we observed only small
changes in plasma AVP levels after dehydration
and
overhydration, these variations were close to those expected during severe changes in hydration states. Indeed,
when our subjects underwent 2 days of water deprivation,
the mean increase in plasma AVP in the six subjects
tested was 1 pg/ml, which corresponds to results of other
groups (21,24), and at the end of the dehydration period,
four of the six donors tested showed plasma AVP levels
between 2.8 and 4.6 pg/ml, values usually obtained when
maximal antidiuresis is achieved (1). On the other hand,
after overhydration the level of AVP decreased significantly but did not fall below the control level, which has
previously been described after drinking in dehydrated
(7) or hypernatremic
humans (26).
We confirm here our previous results showing large
variations in maximal AVP-binding
capacities among
individuals (27). These variations could not result from
methodological
differences, as all experiments were performed using the same experimental
procedure. Moreover, such variations have also been reported by other
groups (12, 25). The range of maximal binding capacity
(42-567 fmol/mg of protein) was much larger than that
observed in other V1 receptor systems where AVP receptors have been shown to be subject to homologous regulation (3, 13). However, the maximal AVP-binding
capacity remained significantly unchanged in each individual during an experimental procedure (dehydration and
overhydration) that produced plasma AVP levels at both
ends of the physiological range, indicating that there is
no relationship
between the number of platelet AVP
receptors and the level of circulating AVP.
Platelet AVP levels also varied greatly among individ-
from
the same experiment;
SC, shape change
only.
Subjects
uals (5.25-35.25 pg/ml), but again this parameter remained quite constant in each individual
during the
dehydration and overhydration periods despite variable
plasma AVP levels. In addition, low values of plasma
AVP were associated with both low and high platelet
AVP levels. These data are consistent with previous
works showing that platelet AVP is unrelated to plasma
AVP (2, 22) and that binding of circulating
AVP to
platelets is observed in vitro only after administration
of
large doses of AVP, far higher than the physiological
plasma AVP fluctuation range. It does not appear that
this platelet-associated
AVP could induce a downregulation of platelet AVP receptors. Indeed low values of
platelet AVP were associated with both high and low
binding capacities, and washing platelets for binding
studies could not have removed residual amounts of AVP
from its binding sites as it has been shown that AVP
binding is not easily reversed (12, 16, 29). The absence
of platelet AVP receptor regulation by platelet-associated
AVP is demonstrated by the lack of correlation between
these two parameters shown in Fig. 2A.
Thus the significance of the platelet-fraction
AVP
remains to be elucidated. This AVP pool has been shown
to be associated with platelet membranes (5), but although AVP binding to platelets is not easily reversed
(29), platelet AVP does not appear to be bound to receptors, because the maximal binding capacity was not
correlated with the amounts of platelet AVP.
Variable platelet responsiveness to AVP in terms of
aggregatory responses was also found in relation to platelet AVP-binding
capacity, confirming
a recent work
showing a relationship between the maximal percentage
of aggregation and the maximal binding capacity of AVP
to intact platelets in normal subjects (12). Two steps in
the homologous downregulation of V, receptors in WRK
1 cells have been described, i.e., a rapid uncoupling step
R1404
HOMOLOGOUS
REGULATION
A
OF
PLATELET
r -0.07
0
0
piatAVP
(PQlml)
0
0
*
A
A
0
*A
.O
I
B
5
4
I
0
I
I
I
1 Om
1
l
1
I =: 0.63
(Pto.01)
A
pAVP
VASOPRESSIN
RECEPTOR
although a significant relationship was observed among
donors, AVP-binding
capacity in the same individual
was a constant unrelated to plasma AVP variations.
Thus it is clear that plasma AVP variations induced by
different hydration states did not result in homologous
regulation at the platelet level over the time investigated.
The observed relationship between these two parameters could be the result of homologous AVP receptor
regulation by variable plasma AVP basal levels, which
affects bone marrow platelet progenitors, i.e., megakaryocytes. Indeed there are individual differences in osmoregulatory
sensitivity that are thought to reflect genetic influences (30) and can induce variable plasma
AVP basal levels. In addition, because platelets are nonnucleated cells and carry only a vestigial protein synthetic apparatus, it is likely that AVP receptors are
actively synthesized by their megakaryocytic precursor
cells (18).
To summarize, in the present investigation
homologous desensitization
or downregulation
of platelet AVP
receptors by plasma AVP or platelet-associated
AVP was
not detectable in vivo at the platelet level within the
physiological range of AVP. Nonetheless, regulation at
the platelet precursor stage remains highly probable.
The authors
are indebted
to the volunteers
who participated
in this
study. We thank the Laboratoire
d’Analyses
Medicales
Francine
Cazaban-Cooper
for taking
blood samples
and Colette
Bellegarde
for
secretarial
assistance.
This work was supported
by the Institut
National
de la Sante et de
la Recherche
Medicale.
Address for reprint
requests: D. Vittet, INSERM
U.300, Faculte de
Pharmacie,
Avenue
Charles
Flahaut,
34060 Montpellier
Cedex
2,
France.
I
100
I
200
I
300
I
I
400
500
1
600
11 October
1988; accepted
in final
form
3 August
1989.
REFERENCES
Bmax
( fmd./mg
Received
protein)
FIG. 2. Relationships
between
B,,, and platAVP
(A) and B,,, and
pAVP (B). All values obtained
with each individual
during control and
different
hydration
stages are plotted, and each symbol corresponds
to
same subject in all graphs. Relationships
were defined by linear regression functions
calculated
by method
of least squares. Relationships
between
different
parameters
were analyzed
using either Student’s
t
test, which implies
a normal
distribution,
or nonparametric
test of
Spearman.
Both tests gave same results, i.e., nonsignificant
relationship between B,,, and platAVP
and significant
relationship
(P c 0.01)
between B max and pAVP.
and a later loss of AVP receptors (4). Nevertheless,
functional platelet aggregatory responses were not significantly changed during variations of plasma AVP after
dehydration in three highly responsive donors or after
drinking in three poorly responsive donors, which excludes the possibility of homologous regulation at the
postreceptor level without any change in the number of
AVP platelet binding sites.
On the other hand, although no variations of maximal
AVP-binding capacity were observed during plasma AVP
variations in the same individual, there was a significant
relationship between plasma AVP and AVP binding capacity, when plotting results of the six subjects tested in
experiment 1 (Fig. ZB). This confirms the apparent homologous regulation of platelet AVP receptors we have
previously reported (14). Nevertheless, as shown above,
and control of vasopressin
secretion
1. BAYLIS, P. H. Osmoregulation
in healthy
humans.
Am. J. Physiol.
253 (Regulatory
Integrative
Comp. Physiol. 22): R671-R678,
1987.
2. BICHET, D. G., M-F. ARTHUS, J-N. BARJON, M. LONERGAN,
AND
C. KORTAS. Human
platelet fraction
arginine-vasopressin.
J. Clin.
Invest. 79: 881-887,
1987.
3. BUTLEN,
D., K. BADDOURI,
R. M. RAJERISON,
G. GUILLON,
B.
CANTAU, AND S. JARD. Plasma antidiuretic
hormone
levels and
liver vasopressin
receptor
in the jerboa, Jaculus orientalis,
and rat.
Gen. Comp. Endocrinol.
54: 216-229,
1984.
4. CANTAU, B., G. GUILLON,
M. FDILI ALAOUI,
D. CHICOT, M. N.
BALESTRE,
AND G. DEVILLIERS.
Evidence
of two steps in the
homologous
desensitization
of vasopressin-sensitive
phospholipase
C in WRKl
cells. J. Biol. Chem. 263: 10443-10450,
1988.
5. CHESNEY, C. M., J. T. CROFTON,
D. D. PIFER, D. P. BROOKS, K.
M. HUCH, AND L. SHARE. Subcellular
localization
of vasopressinlike material
in platelets.
J. Lab. Clin. Med. 106: 314-318,
1985.
6. ERNE, P., AND A. PLETSCHER.
Vasopressin-induced
activation
of
human blood platelets:
prominent
role of Mg?
Naunyn-Schmiedeberg’s Arch. Pharmacol.
329: 97-99, 1985.
GEELEN,
G., L. C. KEIL,
S. E. KRAVIK,
C. E. WADE, T. N.
THRASHER,
P. R. BARNES, G. PYKA, C. NESVIG, AND J. E. GREENLEAF. Inhibition
of plasma vasopressin
after drinking
in dehydrated
humans. Am. J. Physiol. 247 (Regulatory
Integrative
Comp. Physiol.
16): R968-R971,1984.
HALLAM,
T. J., P. A. RUGGLES,
M. C. SCRUTTON,
AND R. B.
WALLIS.
Desensitization
in human
and rabbit
blood platelets.
Thromb.
Haemostasis
47: 278-284,
1982.
HALLAM,
T. J., N. T. THOMPSON,
M. C. SCRUTTON,
AND T. J.
RINK. The role of cytoplasmic
free calcium
in the responses
of
Quin-2
loaded human platelets
to vasopressin.
Biochem.
J. 221:
897-901,
1984.
HOMOLOGOUS
REGULATION
OF PLATELET
10. HASLAM, R. J., AND G. M. ROSSON. Aggregation of human blood
platelets by vasopressin. Am. J. Physiol. 223: 958-967, 1972.
11. HUSAIN,
M. K., N. FERNANDO,
M. SHAPIRO, A. KAGAN, AND S.
M. GLICK. Radioimmunoassay of arginine vasopressin in human
plasma. J. Clin. Endocrinol.
Met. 37: 616-625,
1973.
12. INABA, K., Y. UMEDA, Y. YAMANE, M. URAKAMI, AND M. INADA.
Characterization of human platelet vasopressin receptor and the
relation between vasopressin-induced platelet aggregation and vasopressin binding to platelets. Clin. Endocrinol.
29: 377-386,
1988.
13. KOCH, B., AND B. LUTZ-BUCHER.
Specific receptors for vasopressin
in the pituitary gland: evidence for down-regulation and desensitization to adrenocorticotropin-releasing
factors. Endocrinology
116: 67l-676,
1985.
14. LAUNAY, J.-M., D. VITTET, M. VIDAUD,
A. RONDOT, M.-N. MATHIEU, C. LALAU-KERALY,
B. CANTAU, AND C. CHEVILLARD.
Vlavasopressin specific receptors on human platelets: potentiation by
ADP and epinephrine and evidence for homologous down-regulation. Thromb. Res. 45: 323-331, 1987.
15. LOWRY, 0. H., N. J. ROSEBROUGH,
A. L. FARR, AND R. J. RANDALL. Protein measurement with the Folin phenol reagent. J. Biol.
Chem.
193: 265-275,195l.
16. PLETSCHER, A., P. ERNE, E. BURGISSER, AND F. FERRACIN. Activation of human blood platelets by arginine-vasopressin. Role of
divalent cations. Mol. Pharmacol.
28: 508-514,
1985.
17. POLLOCK,
W. K., AND D. E. MCINTYRE.
Desensitization and
antagonism of vasopressin-induced phosphoinositide metabolism
and elevation of cytosolic free calcium concentration in human
platelets. Biochem. J. 234: 67-73, 1986.
E. M., R. B. LEVENE, L. L. K. LEUNG,
AND R. L.
18. RABELLINO,
NACHMAN.
Human megakaryocytes. II. Expression of platelet proteins in early marrow megakaryocytes. J. Exp. Med. 154: 88-100,
1981.
19. ROBERTSON, G. L., E. A. MAHR, S. ATHAR, AND T. SINHA. The
development and clinical application of a new radioimmunoassay
for arginine-vasopressin in human plasma. J. Clin. Inuest. 52: 23402352,1973.
20. Roos, J., F. FERRACIN,
AND
A. PLETSCHER.
Interaction
of vaso-
VASOPRESSIN
R1405
RECEPTOR
pressin with human blood platelets: dependency on Mg? Thromb.
Haemostusis.
21. SECKL, J.
56: 260-262,
1986.
R., T. D. M. WILLIAMS,
AND S. L. LIGHTMAN.
Oral
hypertonic saline causes transient fall of vasopressin in humans.
Am. J. Physiol.
R214-R217,1986.
22. SHARE, L.,J.T.
251 (Regulatory
Integrative
Comp.
Physiol.
20):
CROFTON,
D.P. BROOKS,AND
CM. CHESNEY.
Platelet and plasma vasopressin in dog during hydration and
vasopressin infusion. Am. J. Physiol. 249 (Regulatory
Integrative
Comp. Physiol. 18): R313-R316, 1985.
23. SIESS, W., M. STIFEL, H. BINDER, AND P. C. WEBER. Activation
of Vl-receptors by vasopressin stimulates inositol phospholipid
hydrolysis and arachidonate metabolism in human platelets.
Biochem. J. 233: 83-91,
24. SORENSEN,
P. S., AND
1986.
M. HAMMER.
Vasopressin in plasma and
ventricular cerebrospinal fluid during dehydration, postural
changes, and nausea. Am. J. Physiol. 248 (Regulatory
Integrative
Comp. Physiol. 17): R78-R83, 1985.
25. THIBONNIER,
M., AND M. WOLOSCHAK.
Platelet aggregation and
vasopressin receptors in patients with Diabetes mellitus. Proc. Sot.
Exp. Biol. Med. 188: 149-152,
1988.
26. THOMPSON,
C. J., J. M. BURD, AND
27.
28.
29.
30.
P. H. BAYLIS. Acute suppression of plasma vasopressin and thirst after drinking in hypernatremic humans. Am. J. Physiol. 252 (Regulatory
Integrative
Comp.
Physiol. 21): R1138-R1142, 1987.
VITTET, D., B. CANTAU, M.-N. MATHIEU,
AND C. CHEVILLARD.
Properties of vasopressin-activated human platelet high affinity
GTPase. Biochem. Biophys. Res. Commun. 154: 213-218, 1988.
VITTET, D., M.-N. MATHIEU,
B. CANTAU, AND C. CHEVILLARD.
Vasopressin inhibition of human platelet adenylate cyclase: variable responsiveness between donors and involvement of a Gprotein different from Gi. Eur. J. Pharmacol.
150: 367-372,
1988.
VITTET,
D., A. RONDOT,
B. CANTAU, J.-M. LAUNAY, AND C.
CHEVILLARD.
Nature and properties of human platelet vasopressin
receptors. Biochem. J. 233: 631-636, 1986.
ZERBE, R. L., AND G. L. ROBERTSON.
Osmoregulation of thirst and
vasopressin secretion in human subjects: effect of various solutes.
Am. J. Physiol. 244 (Endocrinol.
Metab. 7): E607-E614, 1983.