Effects of a Kinin Antagonist on
Mean Blood Pressure
Luis F. CARBONELL, OSCAR A. CARRETERO, PAOLO MADEDDU,
AND A . GUILLERMO SciCLI
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SUMMARY Administration of high doses of a kinin antagonist produces an increase in blood
pressure. Thus, endogenous klnins may be involved in the regulation of blood pressure. Kinins can
induce the release of vasoactive substances such as catecholamines, renin, vasopressin, histamine, and
prostaglandins. To determine whether the blood pressure changes induced by high doses of kinin
antagonist are due to agonistic activity mediated by these vasoactive substances, we studied the effect
on blood pressure of a kinin antagonist (DArg*-Hyp3-Thi54-DPtie7-bradyklnln) administered to control,
nephrectomized, and adrenalectomized rats, and to rats treated with vasopressin V,-receptor
antagonist, ganglionic and a- and /3-adrenergic receptor blockers (either separately or combined),
hl<ifamlnp H,- and Hj-receptor blockers, and indomethacin, a prostaglandin synthesis inhibitor. Blood
pressure changes were monitored on awake, restrained rats. In the control rat, the kinin antagonist
injected as a bolus (4 mg/kg) into the ascending aorta produced a transient biphasic blood
pressure response, first a pressor effect (ABP = 7 ± 1 mm Hg; p<0.05), then a depressor effect
(ABP = - 20 ± 6 mm Hg; p<0.05). The pressor response to the kinin antagonist was not affected by
any of the treatments; however, the depressor effect of the kinin antagonist appeared to be caused by
the release of vasodilator prostanoids from the kidney, since it was not observed in the nephrectomized
rats or in those treated with indomethacin. The pressor effect induced by the kinin antagonist suggests
that kinins may contribute to the regulation of blood pressure.
(Hypertension 11 [Suppl I]: I-84-I-88, 1988)
KEY WORDS
bradykinin • kinin antagonist • Mood pressure regulation • pressor
depressor
mine release from rodent mast cells8 and skin mast
cells,9 and kinins can induce prostaglandin release from
several tissues.10 These effects of kinins and kinin
antagonists could mediate the vasodepressor actions of
high doses of kinin antagonist.
The purposes of this study were to 1) assess the blood
pressure changes induced by the administration of
a new kinin antagonist, DArgo-Hyp3-Thi58-DPhe7bradykinin, and 2) exclude the possibility that these
blood pressure changes are due to mechanisms unrelated to blockade of endogenous kinins such as renin,
vasopressin, catecholamine, histamine, or prostaglandin release.
K
ININS are potent vasodepressor peptides that
appear to be involved as autacoids in the
regulation of normal blood pressure.' Recently, a family of bradykinin analogues having antagonistic properties was synthesized.2 High doses of
one of these kinin antagonists produced both pressor
and depressor effects in normotensive rats.3 However,
kinin antagonists and bradykinin have similar structures, and possibly some of the effects of high doses of
the antagonist were not only due to blocking endogenous kinins, but also related to some agonistic activity.
Kinins can stimulate renin secretion from kidneys4
and vasopressin from the central nervous system,3 as
well as induce catecholamine release from the adrenal
medulla6 and sympathetic ganglia.7 All these actions of
kinins can increase blood pressure. On the other hand,
both kinins and kinin antagonists can produce hista-
Materials and Methods
Bradykinin was purchased from Peninsula Laboratories (Belmont, CA, USA). Kinin antagonist,
D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-DPhe-Thi-Arg-TFA
(Hyp = L-4-hydroxyproline;
Thi = /?-2-thienyl-Lalanine; TFA = trifluoracetic acid), was synthesized
by J. Stewart (Denver, CO, USA) as described
previously.2 Phentolamine (Regitine) was purchased
fromCEBA (Basel, Switzerland). Indomethacin, hexa-
From the Hypertension Research Division, Henry Ford Hospital,
Detroit, Michigan.
Supported in part by grant HL-28982 from the National Institutes
of Health.
Address for reprints: Oscar A. Carretero, M.D., Hypertension
Research Division, Henry Ford Hospital, 2799 Wsst Grand Boulevard, Detroit, MI 48202.
1-84
EFFECTS OF KININ ANTAGONIST ON BLOOD PKESSXJRE/Carbonell et al.
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methonium bromide, propranolol, and nofepinephrine were purchased from Sigma Chemical (St. Louis,
MO, USA). Isoproterenol was purchased from ElkinsSinn (Cherry Hill, NJ, USA), and sodium nitroprusside
from Abbott (Chicago, IL, USA). Arginine vasopressin and the vasopressin V,-receptor antagonist Q3mercapto-/3,/3-cyclopentamethylene-propionic acid,
O-methyl-Tyr2, Arg*) vasopressin were purchased from
Bachem (Torrance, CA, USA). The histamine H,receptor blocker (chlorpheniramine maleate) was purchased from Schering (Kenilworth, NJ, USA), histamine Hj-receptor blocker (cimetidine) was purchased
from SK&F Laboratory (Carolina, Puerto Rico), and
histamine from Eli Lilly (Indianapolis, IN, USA).
All drugs were dissolved with 0.9% NaCl, except
indomethacin, which was dissolved in carbonate
buffer, pH 7.4. The volume of each bolus injection was
0.1 ml, followed by 0.2 ml of 0.9% NaCl solution. The
male Sprague-Dawley rats (230-260 g) used for these
experiments were cared for according to the principles
established in the Guide for the Care and Use of
Laboratory Animals (U.S. Public Health Service). The
rats were housed at a constant room temperature with
a 12-hour light-dark cycle, and had free access to tap
water and rat chow. The surgical maneuvers were
performed with the rats under ether anesthesia. One day
before the experiments, two catheters (PE-50, Clay
Adams, Parsippany, NJ, USA) were inserted into the
rats, one into the ascending aorta through the right
carotid artery for bolus injections, and the other into the
abdominal aorta by way of the left femoral artery for
blood pressure measurement. The catheters were exteriorized in the scapular region as described
previously." During the experiment, the rats were
awake and kept semirestrained in cylindrical plastic
containers. Blood pressure was measured with a
Statham transducer (Gould, Oxford, CA, USA) and
recorded on a Brush recorder (Gould, Cleveland, OH,
USA).
To determine the effectiveness of the bradykinin
blockade, bradykinin (400 ng/kg) was injected both
prior to and after the administration of the kinin
antagonist (4 mg/kg). The 10 experimental groups were
as follows: Group 1, six control rats with no previous
treatment; Group 2, six 24-hour nephrectomized rats;
Group 3, six rats treated with vasopressin antagonist
(30 /Ag/kg); Group 4, six rats treated with a ganglionic
blocker (hexamethonium, 25 mg/kg); Group 5, six
24-hour adrenalectomized rats; Group 6, six 24-hour
adrenalectomized rats treated with hexamethonium
(25 mg/kg); Group 7, six rats treated with a- and
/J-adrenergic receptor blockers (phentolamine, 4
mg/kg, and propranolol, 2 mg/kg); Group 8, six
24-hour nephrectomized and adrenalectomized rats
treated with vasopressin antagonist (30 fig/kg), hexamethonium (25 mg/kg), phentolamine (4 mg/kg), and
propranolol (2 mg/kg); Group 9, six rats treated with
histamine H,- and H2-receptor blockers (chlorpheniramine, 240 /xg/kg, and cimetidine, 16 mg/kg); and
Group 10, Six rats treated with indomethacin (7.5
mg/kg), a blocker of prostaglandin synthesis.
1-85
At the time of adrenalectomy, Groups 4 and 8
received injections of 0.2 mg of deoxycorticosterone
acetate and 1.0 mg of hydrocortisone in oil suspension.
To test whether blood pressure changes from baseline induced by bradykinin and kinin antagonist were
statistically significant, the data were analyzed by
one-sample (paired) t test. Two-sample t tests were used
to determine differences in baseline blood pressure due
to the various treatments. A p value below 0.05 was
considered significant.
Results
Hexamethonium inhibited the increase in heart rate
produced by the hypotensive effect (30 mm Hg) of
sodium nitroprusside (20 /ig/kg) by 88% (80 ± 10 and
10 ± 5 beats/min before and after, respectively; n =
3). Phentolamine inhibited the hypertensive effect of
norepinephrine (2 /xg/kg) by 77% (48 ± 5 and 11 ±
1 mm Hg before and after, respectively; n = 5).
Propranolol inhibited the increase in heart rate produced by isoproterenol (0.8 ^g/kg) by 86% (105 ± 18
and 15 ± 2 beats/min before and after, respectively;
n = 4). The vasopressin antagonist completely
blocked the vasopressor effect of 10 mU of vasopressin (52 ± 2 mm Hg; n = 3). Chlorpheniramine and cimetidine inhibited the depressor effect
of histamine (4 pig/kg) by 55% (18 ± 2 and
8 ± 2 mm Hg before and after, respectively; n = 4).
The kinin antagonist at a dosage of 40 /xg/kg/min
blocked the vasodepressor effect of bradykinin
(400 ng/kg) by 51 ± 4 % . The vasodepressor
effect of sodium nitroprusside (16 /xg) was not
altered (before, 29.6 ± 3 mm Hg; after, 29.2 ± 2 mm
Hg; NS). The concentration of the kinin antagonist
used in the present work was 100-fold more than that
needed to partially block the hypotensive effect of
injected kinins.
The basal mean blood pressure values of the different
experimental groups are shown in Table 1. The
nephrectomized rats (Group 2) had higher blood
TABLE 1. Basal Mean Blood Pressures of the Different Experimental Groups
Blood
pressure
(mm Hg)
Group
1. control
109 + 4
2. nephrectomy
130 + 8*
3. vasopressin antagonist
114 + 4
4. ganglionic blocker
83 + 4*
5. adrenalectomy
99 + 5
81+6*
6. adrenalectomy plus ganglionic blocker
7. a- and /3-blockers
88 + 3*
8. nephrectomy and adrenalectomy plus vasopressin
antagonist and ganglionic and a- and /3-blockers
62 + 9*
113 + 3
9. histamine blockers
10. indomethacin
112 + 3
Values are means + SE.
*p<0.001, compared with the control group.
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INTER-AMERICAN SOCIETY PROCEEDINGS
SUPPL I HYPERTENSION, VOL 11, No 2, FEBRUARY 1988
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Discussion
Kinins are potent vasodepressor peptides that, by
acting as autacoids, may regulate vascular resistance
and consequently, normal blood pressure.1 In the last
few years, many studies assessed the physiological role
of kinins, but the approaches were indirect since no
specific antagonists were available. Recently, a family
of bradykinin analogues having antagonistic properties
was synthesized.2 In this study, we used one of these
kinin antagonists, DArg°-Hyp3-Thi5-8-DPhe7-bradykinin, to determine the role of endogenous kinins on
normal blood pressure maintenance. Low doses of this
kinin antagonist inhibit the vasodepressor effect of
intra-aortically injected bradykinin by more than 50%.
In normal rats, high doses of the antagonist produced
a small but significant increase in blood pressure
followed by a depressor effect. These results agree with
those of Benetos et al.,3 who showed that high doses
of a similar kinin antagonist produced a pressor effect
and also a depressor effect when injected into normal
rats.
Administration of bradykinin produces a biphasic
blood pressure effect: a decrease followed by an
increase." An increase in blood pressure also was
observed when bradykinin was administered into the
carotid artery of the cat12 and dog.13 These findings
suggest that, in addition to its peripheral vasodilator
effect, bradykinin may exert peripheral and central
effects tending to increase blood pressure, which could
pressure (p<0.001) than the control group (Group
1). The blood pressure of the rats treated with ganglionic blocker (Groups 4, 6, and 8) and with a- and
/3-blockers (Group 7) were significantly lower {p<
0.001) than that of the control rats.
In the control group (Figure 1), the bolus injection
of kinin antagonist induced a small pressor effect
followed by a depressor effect, whereas the bolus
injection of bradykinin produced a decrease followed
by a small increase in blood pressure. Both biphasic
responses were transient, and blood pressure returned
to baseline after 1 to 2 minutes. The pressor response
induced by bradykinin was not present in the adrenalectomized rats from Group 5 (Figure 2) and did not
reach statistical significance in the nephrectorriized rats
(Groups 2 and 8; see Figures 1,2, and 3) or in the group
treated with vasopressin V,-receptor antagonist (Group
3; see Figure 2). However, the pressor responses
induced by bolus injection of kinin antagonist were
present in all experimental groups studied (see Figures
1,2, and 3). Bradykinin induced a depressor effect in
all groups, but in the nephrectomized and adrenalectomized rats treated with gangl ionic and a- and
/3-blockers, and with vasopressin antagonist (Group 8;
see Figure 3), this effect did not reach statistical
significance. The depressor effect induced by the kinin
antagonist was blocked by nephrectomy (Groups 2 and
8; see Figures 1 and 3) and by indomethacin (Group 10;
see Figure 3).
Bk
K. Ant.
1
I
2 mln.
A
BKA0YKININ
KININ ANTAOONIST
I
Control
N«phr«ctomiz«d
FIGURE 1. Maximum pressor and depressor effects induced by bolus injections of bradykinin (BK; 400 ng/kg)
and kinin antagonist (K. Ant; 4 mglkg) in control (n = 6) and 24-hour nephrectomized rats (n = 6). Values are
means ± SE (*p < 0.05). Top tracings are examples of actual recordings. In the lower panel, open and closed
circles indicate changes in mean blood pressure from preceding values.
EFFECTS OF KININ ANTAGONIST ON BLOOD PRESSURE/Carbonell et al.
1-87
Adx + Ni + AVP Ant.
+ HtKom«thonlum
+ a k. p Block«ri
a Ji ft Blockars
403020
~ 100 HAffTKIMN
B UMIH AMTAOOJflST
I-IO
-20
-30
-40
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Adr«nal«ctomiz«d
Adx + Ganglionlc
Block.r
FIGURE 2. Maximum pressor and depressor effects induced by
bolus injections ofbradykinin (400 ng/kg) and kinin antagonist
(4 mg/kg) in rats with various treatments. Adx = adrenalectomy. Values are means ± SE (*p < 0.05; n = 6).
be involved in the biphasic or pressor response described previously.
Kinins can stimulate renin secretion from the kidney4
and vasopressin from the central nervous system,3 as
well as release catecholamines from the adrenal
medulla6 and sympathetic ganglia.7 In our study, the
pressor response induced by bradykinin was not present
in adrenalectomized rats and was negligible in nephrectomized rats and in the group treated with vasopressin V,-receptor antagonist. These results suggest
that the vasopressor response to bradykinin is mediated
by the release of vasopressor hormones from several
sources. In contrast, the vasopressor action of the kinin
antagonist cannot be explained by this mechanism,
since it was present in all experimental groups. Thus,
it is likely that the vasopressor actions of the kinin
antagonist are due to inhibition of the vasodepressor
activity of endogenous kinins, although a direct cardiovascular effect of high doses of the kinin antagonist
cannot be completely ruled out.
The mechanisms mediating the vasodepressor actions of the kinin antagonist and of bradykinin appear
to be different. The vasodepression induced by the
kinin antagonist was not observed in nephrectomized
rats or in indomethacin-treated rats. Thus, the hypotensive effects of the kinin antagonist appear to be due
to the release of vasodilating prostanoids from the
kidney. Kinins can release prqstaglandins from a
variety of tissues, including the kidney.10 It could be
that at the dose administered, the kinin antagonist
induced prostaglandin synthesis by a kininlike agonistic activity on renal receptors. It cannot be ruled out that
the hypotensive response induced by the kinin antagonist may be due to an effect related to impurities
present in the preparation when administered at a high
U-A
\
» MtAOYKIMH
» K1WH AMTMOIUST
I
_i
Hlttamln* Blockari
Indomtthacln
FIGURE 3. Maximum pressor and depressor effects induced by
bolus injection of bradykinin (400 ng/kg) and kinin antagonist
(4 mg/kg) in rats with various treatments. Nx = nephrectomy;
Adx = adrenalectomy; AVP Ant = vasopressin V,-receptor
antagonist. See Materials and Methods for doses. Values are
means ± SE (*p < 0.05; a = 6).
dose. We are not aware, however, of the presence of contaminants in the synthetic kinin antagonist preparation.
The results show that bradykinin causes a vasodepressor effect by a direct action on peripheral vessels,
which may be mediated by the release of endothelialderived relaxing factor.14 At the dose of bradykinin
used, release of prostanoids from the kidneys did not
appear to contribute to its vasodepressor activity.
We conclude that the depressor effects of the kinin
antagonist may be due to agonistic action. The pressor
effect induced by kinin antagonist suggests that endogenous kinins may contribute to the maintenance of
normal blood pressure.
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Effects of a kinin antagonist on mean blood pressure.
L F Carbonell, O A Carretero, P Madeddu and A G Scicli
Hypertension. 1988;11:I84
doi: 10.1161/01.HYP.11.2_Pt_2.I84
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