Role of endothelin receptors in the hypertensive state of kinin B2 knockout mice subjected to a high-salt diet

2002 ◽  
Vol 103 (s2002) ◽  
pp. 380S-384S ◽  
Author(s):  
Isabelle BROCHU ◽  
Julie LABONTÉ ◽  
Ghassan BKAILY ◽  
Pedro D'ORLÉANS-JUSTE
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Receptor Antagonist ◽  
Tap Water ◽  
Blood Pressure Measurement ◽  
Rna Extraction ◽  
Angiotensin Receptors ◽  
Rt Pcr ◽  
Arterial Blood

Mice with disruption of the kinin B2 receptor (B2KO mice) are sensitive to salt-rich diets, which causes hypertension. The aim of the study was to assess the role of endothelin-1 (ET-1) and angiotensin-II in hypertensive B2KO mice on a salt-rich diet. We also wanted to verify if there is an upregulation of the mRNA expression of the precursors or receptors for these hormones. Two groups of B2KO mice (20–25g) were investigated. The first group received an 8% NaCl diet with 1% NaCl in drinking water (HS) and the second was fed with normal food with tap water (NS). The antagonists tested were the ETA receptor antagonist BQ-123 (1 and 5mg/kg), the ETB receptor antagonist BQ-788 (0.25 and 1mg/kg), the angiotensin receptor type 1 antagonist losartan (10mg/kg) and the angiotensin-converting enzyme inhibitor captopril (3mg/kg). These were injected intraperitoneally 30min prior to blood pressure measurement by the tail-cuff method. We also studied the level of expression of preproET-1, ET-1 receptors, angiotensinogen and angiotensin receptors by RNA extraction from the heart and kidneys of these mice followed by reverse transcriptase (RT)-PCR. B2KO mice (HS) were hypertensive after 8 weeks compared with B2KO mice on normal diet (HS, 93.4±1.5mmHg, n = 7; NS, 61.4±2.7mmHg, n = 7). In the HS group, the mean arterial blood pressure was significantly reduced by BQ-123 (5mg/kg) to 61.9±1.8mmHg (n = 7), by BQ-788 (1mg/kg) to 58.8±2.6mmHg (n = 6), by losartan (10mg/kg) to 73.2±1.7mmHg (n = 8) and by captopril (3mg/kg) to 86.0±2.3mmHg (n = 8). The expression studied by RT-PCR did not show any difference (either in precursors or receptors expression) between hypertensive and normal mice. The four antagonists used seemed to reverse the hypertension. These results suggest that ET-1 and angiotensin-II are probably involved in the mechanism that leads to hypertension since the effect of these hormones is probably not compensated by kinins in B2KO mice. Further studies are necessary to understand the implication of the cross-talk between these hormones in the hypertensive state.

Increased central AT1-receptor activation, not systemic vasopressin, sustains hypertension in ANP knockout mice

2000 ◽  
Vol 278 (6) ◽  
pp. R1441-R1445 ◽  
Author(s):  
Uwe Ackermann ◽  
Newsha Azizi
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Receptor Antagonist ◽  
Knockout Mice ◽  
Blood Pressure Measurement ◽  
Receptor Activation ◽  
Wild Type ◽  
Vasopressin Release ◽  
Arterial Blood ◽  
Left Lateral Ventricle

We tested the hypothesis that hypertension in atrial natriuretic peptide (ANP) knockout mice is caused in part by disinhibition of angiotensin II-mediated vasopressin release. Inactin-anesthetized F2 homozygous ANP gene-disrupted mice (−/−) and wild-type (+/+) littermates were surgically prepared for carotid arterial blood pressure measurement (ABP) and background intravenous injection of physiological saline or vasopressin V1-receptor antagonist (Manning compound, 10 ng/g body wt) and subsequent intracerebroventricular (left lateral ventricle) injection of saline (5 μl) or ANP (0.5 μg) or angiotensin II AT1-receptor antagonist losartan (10 μg). Only (−/−) showed significant decrease in ABP after intracerebroventricular ANP or losartan. Both showed significant hypotension after intravenous V1 antagonist, but there was no difference between their responses. We conclude that 1) vasopressin contributes equally to ABP maintenance in ANP-disrupted mice and wild-type controls; 2) permanently elevated ABP in ANP knockouts is associated with increased central nervous angiotensin II AT1-receptor activation; 3) disinhibition of central nervous angiotensin II AT1receptors in ANP-deficient animals does not lead to a significant increase in the importance of vasopressin as a mechanism for blood pressure maintenance.

Role of arteria baroreceptor input on thirst and urinary responses to intracerebroventricular angiotensin II

1993 ◽  
Vol 265 (3) ◽  
pp. R591-R595 ◽  
Author(s):  
R. L. Thunhorst ◽  
S. J. Lewis ◽  
A. K. Johnson
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Arterial Blood Pressure ◽  
Water Intake ◽  
Enzyme Inhibitor ◽  
Ang Ii ◽  
Converting Enzyme ◽  
Arterial Blood ◽  
Endogenous Formation

Intracerebroventricular (icv) infusion of angiotensin II (ANG II) in rats elicits greater water intake under hypotensive, compared with normotensive, conditions. The present experiments used sinoaortic baroreceptor-denervated (SAD) rats and sham-operated rats to examine if the modulatory effects of arterial blood pressure on water intake in response to icv ANG II are mediated by arterial baroreceptors. Mean arterial blood pressure (MAP) was raised or lowered by intravenous (i.v.) infusions of phenylephrine (1 or 10 micrograms.kg-1 x min-1) or minoxidil (25 micrograms.kg-1 x min-1), respectively. The angiotensin-converting enzyme inhibitor captopril (0.33 mg/min) was infused i.v. to prevent the endogenous formation of ANG II during testing. Urinary excretion of water and solutes was measured throughout. Water intake elicited by icv ANG II was inversely related to changes in MAP. Specifically, rats drank more water in response to icv ANG II when MAP was reduced by minoxidil but drank less water when MAP was elevated by phenylephrine. The influence of changing MAP on the icv ANG II-induced drinking responses was not affected by SAD. These results suggest that the modulatory effects of arterial blood pressure on icv ANG II-induced drinking can occur in the absence of sinoaortic baroreceptor input.

Support of arterial blood pressure by major pressor systems in conscious dogs

1988 ◽  
Vol 255 (3) ◽  
pp. H483-H491 ◽  
Author(s):  
P. H. Brand ◽  
P. J. Metting ◽  
S. L. Britton
Keyword(s):  
Blood Pressure ◽  
Nervous System ◽  
Steady State ◽  
Autonomic Nervous System ◽  
Angiotensin Ii ◽  
Arterial Blood Pressure ◽  
Autonomic Function ◽  
Autonomic Ganglia ◽  
Arterial Blood

The roles of the autonomic nervous system, vasopressin, and angiotensin II in support of blood pressure were evaluated in seven conscious, resting dogs while hydrated or dehydrated. Mean arterial blood pressure (MAP) was monitored, and the dogs were given hexamethonium to block autonomic ganglia. Thirty minutes later, they were given captopril, and after another 30 min, a vasopressin V1 antagonist, d(CH2)5TyrMeAVP, was given. The order okf administration of captopril and d(CH2)5TyrMeAVP was alternated in different experiments. Hexamethonium had no effect on steady-state MAP in either hydrated or dehydrated dogs. In hydrated dogs, the average MAP was 100 mmHg; d(CH2)5TyrMeAVP decreased MAP by approximately 12 mmHg, and captopril decreased MAP by 24 mmHg. The magnitude of the effect of these two inhibitors was independent of the order of their administration. Dehydration doubled the effect of d(CH2)5TyrMeAVP on MAP but had no effect on the response to captopril. The results suggest that 1) autonomic function is not essential for maintenance of arterial blood pressure in resting dogs; 2) during autonomic ganglionic blockade, arterial blood pressure is supported by both angiotensin II and vasopressin; and 3) dehydration increases the role of vasopressin in control of blood pressure.

Role of vasoconstrictors in the systemic hypertension of rats acclimatized to hypoxia

1995 ◽  
Vol 79 (5) ◽  
pp. 1657-1667 ◽  
Author(s):  
Y. Moue ◽  
P. G. Smith ◽  
R. L. Clancy ◽  
N. C. Gonzalez
Keyword(s):  
Blood Pressure ◽  
Smooth Muscle ◽  
Angiotensin Ii ◽  
Sodium Nitroprusside ◽  
Barometric Pressure ◽  
Systemic Hypertension ◽  
Ang Ii ◽  
Arterial Blood ◽  
Smooth Muscle Relaxant

Exposure to hypoxia (2–5 wk) results in systemic hypertension in rats and in humans. The possible mechanism(s) was investigated in rats acclimatized for 3 wk to barometric pressure of approximately 370 Torr (A) and in nonacclimatized littermates (NA) by administration of alpha-adrenergic [phentolamine (PHLM)], angiotensin II (ANG II), and arginine vasopressin (AVP V1) receptor antagonists. Both A and NA rats were studied in hypoxia (inspiratory O2 fraction = 0.10). Baseline mean arterial blood pressure (MABP) was higher in A than in NA rats: 126 +/- 4 vs. 101 +/- 2 mmHg (P < 0.05). Neither ANG II nor AVP V1 receptor antagonist influenced baseline MABP; however, both contributed to MABP recovery after PHLM. After simultaneous blockade of ANG II and AVP V1, PHLM lowered MABP by 65 +/- 2 and 45 +/- 3 mmHg in A and NA rats, respectively (P < 0.05). After combined blockade of the three systems, the smooth muscle relaxant sodium nitroprusside did not further modify MABP, which remained higher in A rats. It is concluded that 1) the hypertension in A rats is partly due to a higher alpha-adrenergic tone, 2) neither ANG II nor AVP contributes to the hypertension, but ANG II and AVP participate in MABP control after PHLM, 3) no other vasoconstrictor agents operate in either group, and 4) the higher MABP in A rats after sodium nitroprusside may reflect additional hypertensive mechanisms.

Chronic angiotensin II AT1 receptor blockade increases cerebral cortical microvessel density

2006 ◽  
Vol 290 (2) ◽  
pp. H512-H516 ◽  
Author(s):  
Diane H. Munzenmaier ◽  
Andrew S. Greene
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Arterial Blood Pressure ◽  
Microvessel Density ◽  
Day Treatment ◽  
Blood Pressure Measurement ◽  
Receptor Blockade ◽  
Independent Manner ◽  
Indwelling Catheters ◽  
Arterial Blood

Angiotensin II is known to stimulate angiogenesis in the peripheral circulation through activation of the angiotensin II type 1 (AT1) receptor. This study investigated the effect of angiotensin receptor blockade on cerebral cortical microvessel density. Rats (6–7 wk old, n = 5–17) were instrumented with femoral arterial and venous indwelling catheters for arterial blood pressure measurement and drug administration. Rats were treated for 3 or 14 days with the AT1 receptor blocker losartan (50 mg/day in drinking water) or vehicle. Brains were sectioned and immunostained for CD31, and microvessel density was measured. Treatment with losartan for 3 or 14 days resulted in a slight decrease in mean arterial blood pressure (3 days, 92 ± 1 mmHg; and 14 days, 99 ± 2 mmHg) compared with vehicle (109 ± 3 and 125 ± 4 mmHg, respectively). A furosemide + captopril 14-day treatment group was added to control for the blood pressure change (96 ± 3 mmHg). Microvessel density increased in groups treated with losartan for 14 days (429 ± 13 vessels/mm2) compared with vehicle (383 ± 11 vessels/mm2) but did not change with furosemide + captopril (364 ± 7 vessels/mm2). Thus AT1 receptor blockade for 14 days resulted in increased cerebral microvessel density in a blood pressure-independent manner.

Role of dopamine in the angiotensin II-induced vasopressin release in the conscious dehydrated dog

1982 ◽  
Vol 94 (2) ◽  
pp. 243-249 ◽  
Author(s):  
D. P. Brooks ◽  
J. R. Claybaugh
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Plasma Renin Activity ◽  
Mean Arterial Blood Pressure ◽  
Arginine Vasopressin ◽  
Plasma Renin ◽  
Dopamine Antagonist ◽  
Vasopressin Release ◽  
Arterial Blood

The effect of the dopamine antagonist, haloperidol, on arginine-vasopressin (AVP) release induced by angiotensin II was studied in six dehydrated conscious dogs. Angiotensin II (10 ng/kg per min) alone caused a twofold increase (P<0·05) in plasma AVP concentration, a 25 mmHg increase (P<0·01) in mean arterial blood pressure (ABP) and a 70% decrease (P<0·01) in plasma renin activity (PRA). In the presence of haloperidol (3 μg/kg per min), angiotensin II caused similar changes in mean ABP (+25 mmHg; P<0·01) and PRA (−65%, P<0·01), but a small insignificant decrease in plasma AVP (−22%). The AVP response to angiotensin II in the presence of haloperidol was significantly (P<0·05) different from its response to angiotensin II alone. Neither haloperidol alone nor the two vehicles had any effect on plasma AVP or mean ABP but PRA dropped slightly. The results suggest that a dopaminergic mechanism may be involved in angiotensin II-induced AVP release.

Role of the area postrema in angiotensin II modulation of baroreflex control of heart rate in conscious mice

2003 ◽  
Vol 284 (3) ◽  
pp. H1003-H1007 ◽  
Author(s):  
Baojian Xue ◽  
Hope Gole ◽  
Jaya Pamidimukkala ◽  
Meredith Hay
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Angiotensin Ii ◽  
Arterial Pressure ◽  
Area Postrema ◽  
Ang Ii ◽  
Baroreflex Control ◽  
Arterial Blood ◽  
Intravenous Infusions

This study reports the effects of angiotensin II (ANG II), arginine vasopression (AVP), phenylephrine (PE), and sodium nitroprusside (SNP) on baroreflex control of heart rate in the presence and absence of the area postrema (AP) in conscious mice. In intact, sham-lesioned mice, baroreflex-induced decreases in heart rate due to increases in arterial pressure with intravenous infusions of ANG II were significantly less than those observed with similar increases in arterial pressure with PE (slope: −3.0 ± 0.9 vs. −8.1 ± 1.5 beats · min−1 · mmHg−1). Baroreflex-induced decreases in heart rate due to increases in arterial pressure with intravenous infusions of AVP were the same as those observed with PE in sham animals (slope: −5.8 ± 0.7 vs. −8.1 ± 1.5 beats · min−1 · mmHg−1). After the AP was lesioned, the slope of baroreflex inhibition of heart rate was the same whether pressure was increased with ANG II, AVP, or PE. The slope of the baroreflex-induced increases in heart rate due to decreases in arterial blood pressure with SNP were the same in sham- and AP-lesioned animals. These results indicate that, similar to other species, in mice the ability of ANG II to acutely reset baroreflex control of heart rate is dependent on an intact AP.

Effect of angiotensin II and of an Angiotensin II Analogue (Sar1-Ile8-Angiotensin II) on Blood Pressure, Plasma Aldosterone and Plasma Renin Activity in the Dog

1974 ◽  
Vol 48 (s2) ◽  
pp. 41s-44s
Author(s):  
R. Beckerhoff ◽  
G. Uhlschmid ◽  
W. Vetter ◽  
H. Armbruster ◽  
J. Nussberger ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Plasma Renin Activity ◽  
Arterial Blood Pressure ◽  
Plasma Renin ◽  
Plasma Aldosterone ◽  
Renin Activity ◽  
Angiotensin Receptors ◽  
Pressure Plasma ◽  
Arterial Blood

1. The effect of infusions of equimolar doses of angiotensin II (AII) and of the angiotensin analogue Sar1-Ile8-angiotensin II on arterial blood pressure, plasma aldosterone and plasma renin activity were compared in normal anaesthetized dexamethasone suppressed dogs. 2. Angiotensin II induced a significant increase of blood pressure and of plasma aldosterone whereas plasma renin activity decreased. The blood pressure was only slightly affected by large doses of the analogue. Plasma aldosterone, however, increased and plasma renin activity decreased. These changes were significant but less pronounced than after the infusions of angiotensin II. Plasma aldosterone remained high and renin activity low for 40 min after the infusions of the analogue. 3. The results suggest a strong agonistic potency of Sar1-Ile8-angiotensin II at the adrenal and renal angiotensin receptors, and that it is almost ineffective at the vascular receptors. The inhibition of renin secretion by angiotensin seems not to be related to its vasoconstrictive activity.

Olmesartan Medoxomil: The Seventh Angiotensin Receptor Antagonist

2003 ◽  
Vol 37 (1) ◽  
pp. 99-105 ◽  
Author(s):  
Stephanie F Gardner ◽  
Amy M Franks
Keyword(s):  
Blood Pressure ◽  
Clinical Trials ◽  
Angiotensin Ii ◽  
Adverse Effects ◽  
Receptor Antagonist ◽  
Olmesartan Medoxomil ◽  
Data Sources ◽  
Angiotensin Receptors ◽  
Angiotensin Receptor ◽  
Angiotensin Ii Receptor

OBJECTIVE To review the pharmacology, pharmacokinetics, efficacy, and adverse effects of olmesartan medoxomil, an angiotensin II receptor antagonist for the treatment of hypertension. DATA SOURCES Information was obtained from MEDLINE searches (1996–April 2002) of English-language medical literature. Search terms included CS-866, olmesartan, olmesartan medoxomil, RNH-6270 (active metabolite of olmesartan), Benicar, angiotensin receptors, and antihypertensive agents. In addition, references from relevant articles were reviewed for additional citations. The authors independently reviewed literature identified in the searches. Studies evaluating olmesartan (i.e., abstracts, clinical trials, data on file with manufacturer) were considered for inclusion. STUDY SELECTION All articles identified from data sources with pertinent information regarding olmesartan medoxomil were evaluated, and all information deemed relevant was included in this review. DATA SYNTHESIS Olmesartan medoxomil is a competitively priced addition to the class of angiotensin II receptor antagonists. Monotherapy with olmesartan medoxomil in once-daily doses of 20–40 mg has produced significant reductions in systolic and diastolic blood pressure in hypertensive patients. Adverse effects have been minimal with olmesartan medoxomil, with dizziness being the only adverse effect occurring more often than with placebo in clinical trials. Additionally, animal studies indicate that olmesartan medoxomil may prove to be useful treatment for diabetic nephropathy, as well as atherosclerosis. CONCLUSIONS Olmesartan medoxomil has a favorable safety and efficacy profile, with blood pressure–lowering effects comparable to those of other angiotensin receptor blockers (i.e., losartan, valsartan, irbesartan). At this time, formulary decisions will be driven primarily by economic issues. Theoretical benefits of olmesartan medoxomil in reducing atherogenesis and lowering angiotensin II concentrations better than the alternative agents will be determined only with more extensive research. THIS ARTICLE IS APPROVED FOR CONTINUING EDUCATION CREDIT ACPE UNIVERSAL PROGRAM NUMBER: 407-000-03-002-H01

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