Effect of Sodium Depletion on the Steroidogenic and Pressor Actions of Angiotensin in the Rat

1. To investigate the relative roles of angiotensin II (AII) and des-Asp1-angiotensin II (angiotensin III) in the control of blood pressure and aldosterone release, the effects of seven angiotensin agonists on mean arterial blood pressure and serum aldosterone concentrations were compared in normal and sodium-depleted, conscious rats. 2. In normal rats, angiotensin I, α-Asp1-angiotensin II, β-Asp1-angiotensin II, and angiotensin II-amide were equipotent in elevating mean arterial blood pressure. Angiotensin III, des-Asp1-angiotensin I, and poly-O-acetylserine-angiotensin II were 25%, 25%, and 41% as potent as angiotensin II, respectively. After sodium depletion, pressor responses to these angiotensin peptides were reduced approximately 60–80% when compared with control responses. In contrast, pressor responses to noradrenaline were not significantly affected by sodium depletion. 3. Angiotensin II, β-Asp1-angiotensin II, angiotensin II-amide, and angiotensin III were equipotent in increasing serum aldosterone concentrations in normal animals. Angiotensin I was 59% and des-Asp1-angiotensin I only 5% as potent as angiotensin II in their abilities to release aldosterone. After sodium depletion, control serum aldosterone concentrations increased as did the slope of the dose—response curve for each angiotensin peptide. Angiotensin II was the most potent steroidogenic peptide in sodium-depleted rats with angiotensin III and β-Asp1-angiotensin II being 27%, angiotensin I 7%, angiotensin II-amide 3%, and des-Asp1-angiotensin I 1% as potent as angiotensin II in releasing aldosterone. Poly-O-acetylserine-angiotensin II has less steroidogenic effect than angiotensin II or III in both normal and sodium-depleted animals. 4. Infusions of the angiotensin II antagonist, Sar1-Ile8-angiotensin II, and the angiotensin III antagonist, Ile7-angiotensin III, enhanced aldosterone release in normal rats without altering blood pressure. After sodium depletion, Sar1-Ile8-angiotensin II decreased blood pressure without affecting aldosterone release whereas Ile7-angiotensin III diminished aldosterone release without altering blood pressure. 5. These data suggest that angiotensin II, independent of its conversion into angiotensin III, is an important regulator of steroidogenesis in the rat in normal sodium states. In sodium depletion, the octapeptide retains significant steroidogenic activity; however, the contribution of angiotensin III to its steroidogenic effects is increased.

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Effects of the angiotensin II receptor antagonist Losartan (DuP 753/MK 954) on arterial blood pressure, heart rate, plasma concentrations of angiotensin II and renin and the pressor response to infused angiotensin II in the salt-deplete dog

Clinical Science ◽

10.1042/cs0830549 ◽

1992 ◽

Vol 83 (5) ◽

pp. 549-556 ◽

Cited By ~ 13

Author(s):

R. J. MacFadyen ◽

M. Tree ◽

A. F. Lever ◽

J. L. Reid

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Angiotensin Ii ◽

Arterial Pressure ◽

Arterial Blood Pressure ◽

Mean Arterial Blood Pressure ◽

Pressor Response ◽

Arterial Blood ◽

Pressor Responses ◽

Plasma Angiotensin

1. The blood pressure, heart rate, hormonal and pressor responses to constant rate infusion of various doses of the angiotensin (type 1) receptor antagonist Losartan (DuP 753/MK 954) were studied in the conscious salt-deplete dog. 2. Doses in the range 0.1–3 μmin−1 kg−1 caused no change in blood pressure, heart rate or pressor response to angiotensin II (54 ng min−1kg−1), and a dose of 10 μgmin−1 kg−1 had no effect on blood pressure, but caused a small fall in the pressor response to angiotensin II. Infusion of Losartan at 30 μmin−1 kg−1 for 3 h caused a fall in mean blood arterial pressure from baseline (110.9 ± 11.2 to 95.0 ± 12.8 mmHg) and a rise in heart rate (from 84.6 ± 15.1 to 103 ± 15.2 beats/min). Baseline plasma angiotensin II (42.5 ± 11.8 pg/ml) and renin (64.5 ± 92.7 μ-units/ml) concentrations were already elevated in response to salt depletion and rose significantly after Losartan infusion to reach a plateau by 70 min. The rise in mean arterial blood pressure after a test infusion of angiotensin II (35.3 ± 11.6 mmHg) was reduced at 15 min (11.8 ± 6.8 mmHg) by Losartan and fell progressively with continued infusion (3 h, 4.3 ± 3.3 mmHg). The peak plasma angiotensin II concentration during infusion of angiotensin II was unaffected by Losartan, but the rise in plasma angiotensin II concentration during infusion was reduced because of the elevated background concentration. Noradrenaline infusion caused a dose-related rise in mean blood arterial pressure (1000 ngmin−1kg−1, +19.9 ± 8 mmHg; 2000ngmin−1 kg−1, +52.8 ± 13.9 mmHg) with a fall in heart rate (1000 ng min−1 kg−1, −27.9 ± 11.5 beats/min; 2000 ng min−1 kg−1, −31.2 ± 17.3 beats/min). During Losartan infusion the 1000 but not the 2000 ng min−1 kg−1 noradrenaline infusion caused a greater rise in mean arterial blood pressure and a greater fall in heart rate. The fall in heart rate tended to decrease with continued infusion of Losartan. Plasma catecholamine concentrations were unaffected by Losartan. In a further study, higher doses of Losartan (100, 300 and 1000 μg min−1 kg−1; 30 min) produced greater falls in mean arterial blood pressure also with a rise in heart rate and complete blockade of the pressor effect of infused angiotensin II. Some animals became disturbed at the highest dose. 3. Losartan produces rapid dose-related falls in blood pressure and a rise in heart rate and renin release with elevation of plasma angiotensin II. Pressor responses to angiotensin II are reduced at intermediate doses and are eliminated at high doses. Losartan does not appear to inhibit angiotensin II clearance from the plasma and may in some way increase it.

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The Effect of Captopril on Blood Pressure and Angiotensins I, II and III in Sodium-Depleted Dogs: Problems Associated with the Measurement of Angiotensin II after Inhibition of Converting Enzyme

Clinical Science ◽

10.1042/cs0580445 ◽

1980 ◽

Vol 58 (6) ◽

pp. 445-450 ◽

Cited By ~ 26

Author(s):

J. J. Morton ◽

M. Tree ◽

J. Casals-Stenzel

Keyword(s):

Blood Pressure ◽

Angiotensin Ii ◽

Fold Increase ◽

Converting Enzyme ◽

Angiotensin I ◽

Active Inhibitor ◽

Arterial Blood ◽

Rapid Fall ◽

Angiotensin Iii ◽

Plasma Angiotensin

1. Changes in arterial blood pressure, blood angiotensin I, plasma angiotensin II and plasma angiotensin III were measured in conscious sodium—depleted dogs after infusion of captopril, an orally active inhibitor of converting enzyme. 2. Angiotensins II and III were measured after chromatography to remove angiotensin I, which increased in concentration after inhibition of converting enzyme and which interfered in the direct assay for angiotensin II. 3. Infusion of captopril at 20, 200, 2000 and 6000 μg h−1 kg−1, each for 3 h, produced a rapid fall in blood pressure and in concentration of angiotensin II. Angiotensin II was undetectable at 6000 μg h−1 kg−1 (mean pre-infusion value for all samples was 39 ± sd 15 pmol/I, n = 14) 4. The percentage fall in blood pressure correlated with the percentage fall in plasma angiotensin II (r = 0.65, P<0.001) 5. These results suggest that the initial fall in blood pressure may be mediated in part by the suppression of angiotensin II. 6. Blood angiotensin I concentration rose with each rate of infusion of drug to a maximum 16-fold increase at 6000 μg h−1 kg−1 (26−416 pmol/l). The rise in angiotensin I was inversely related to the fall in angiotensin II (r = −0.68, P<0.001)

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Physiological Amounts of Angiotensinogen Increase Blood Pressure in Sprague Dawley Rats After I.V. Administration.

Hypertension ◽

10.1161/hyp.36.suppl_1.694-d ◽

2000 ◽

Vol 36 (suppl_1) ◽

pp. 694-694

Author(s):

Christoph P R Klett ◽

Joey P Granger

Keyword(s):

Blood Pressure ◽

Arterial Blood Pressure ◽

Transit Time ◽

Mean Arterial Blood Pressure ◽

Time Lag ◽

Plasma Concentrations ◽

Sprague Dawley ◽

Angiotensin I ◽

Arterial Blood ◽

Sprague Dawley Rats

P9 The synthesis and secretion of hepatic angiotensinogen is controlled by a complex pattern of physiologic and pathophysiologic mediators including glucocorticoids, estrogens, thyroid hormones, cytokines, glucagon,insulin, and prostaglandins. Since plasma concentrations of angiotensinogen are close to the Michaelis Menten constant, it was hypothesized that changes in angiotensinogen plasma concentrations have an influence on the formation rate of angiotensin I and angiotensin II and, therefore, on blood pressure. To further test this hypothesis we injected purified rat angiotensinogen i.v. in Sprague Dawley rats via the femoral vein. Mean arterial blood pressure was measured after arterial cathederization. Control animals had a mean arterial pressure of 131 ± 2 mm Hg before and after the injection of vehicle (saline). The injection of 0.8, 1,2, and 2.9 mg/kg angiotensinogen caused a dose dependend increase in mean arterial blood pressure of 8 ± 0.4, 19.3 ± 2.1, and 32 ± 2.4 mm Hg, respectively. In contrast, the injection of a purified rabbit anti-rat-angiotensinogen antibody 1.4 mg/kg resulted in a significant decrease in blood pressure (-52 ± 3.2 mmHg). In an attempt to analyze how fast and efficient angiotensinogen production can sense regulatory input and convert into adaptation of secretion rate we determined the transit time (time needed for translation and post-translational modifications) for angiotensinogen in a pulse chase experiment employing 35 [S]-methionine as label in freshly isolated hepatocytes. During the chase periode, after quantitative immunoprecipitation, we determined the transit time for angiotensinogen with 2.5 h which is consistent with the constitutive type of angiotensinogen secretion and the time lag found for plasma concentrations to respond to regulatory mediators. In summary we conclude that variations in angiotensinogen plasma concentrations can result in changes in blood pressure. In contrast to renin known as a tonic regulator for the generation of angiotensin I, angiotensinogen seems to be a factor rather important for long-term control of the basal activity of the renin angiotensin system.

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Cardiac hypertrophy in Aryl hydrocarbon receptor null mice is correlated with elevated angiotensin II, endothelin-1, and mean arterial blood pressure

Toxicology and Applied Pharmacology ◽

10.1016/j.taap.2003.08.008 ◽

2003 ◽

Vol 193 (2) ◽

pp. 177-187 ◽

Cited By ~ 94

Author(s):

Amie K Lund ◽

M.Beth Goens ◽

Nancy L Kanagy ◽

Mary K Walker

Keyword(s):

Blood Pressure ◽

Angiotensin Ii ◽

Cardiac Hypertrophy ◽

Aryl Hydrocarbon Receptor ◽

Arterial Blood Pressure ◽

Mean Arterial Blood Pressure ◽

Endothelin 1 ◽

Aryl Hydrocarbon ◽

Arterial Blood

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Plasma vasopressin in blood pressure homeostasis and in experimental renal hypertension

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1980.239.1.h81 ◽

1980 ◽

Vol 239 (1) ◽

pp. H81-H87 ◽

Cited By ~ 2

Author(s):

P. T. Pullan ◽

C. I. Johnston ◽

W. P. Anderson ◽

P. I. Korner

Keyword(s):

Blood Pressure ◽

Angiotensin Ii ◽

Arterial Blood Pressure ◽

Mean Arterial Blood Pressure ◽

Pressor Response ◽

Renal Hypertension ◽

Similar Degree ◽

Arterial Blood ◽

Plasma Vasopressin ◽

Experimental Renal Hypertension

The role of vasopressin in blood pressure control and in the pathogenesis of one-kidney Goldblatt hypertension was investigated in the conscious dog. Intravenous infusion of synthetic arginine vasopressin to elevate plasma levels approximately fivefold to 31 pg/ml caused bradycardia in normal dogs, together with suppression of plasma renin activity and angiotensin II. This plasma level of vasopressin also caused elevation of mean arterial blood pressure in dogs with pharmacological total autonomic blockade. A similar degree of elevation of plasma vasopressin concentration was observed following mild nonhypotensive hemorrhage; more severe hemorrhage resulted in an approximate 100-fold increase in plasma vasopressin levels. Severe renal artery constriction in unilaterally nephrectomized dogs caused a marked rise in mean arterial blood pressure, but only a doubling of plasma vasopressin concentration. A suppressor infusion of vasopressin did not potentiate the pressor response to infused angiotensin II. It is concluded that vasopressin may play a role in normal cardiovascular homeostatic responses, but it is unlikely to have a significant direct vasoconstrictor role in the pathogenesis of this form of experimental renal hypertension.

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Sex differences in central cholinergic and angiotensinergic control of vasopressin release

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1992.263.5.r1030 ◽

1992 ◽

Vol 263 (5) ◽

pp. R1030-R1034 ◽

Cited By ~ 3

Author(s):

J. D. Stone ◽

J. T. Crofton ◽

L. Share

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Angiotensin Ii ◽

Estrous Cycle ◽

Arterial Blood Pressure ◽

Mean Arterial Blood Pressure ◽

Female Rats ◽

Vasopressin Release ◽

Arterial Blood ◽

Plasma Vasopressin

In conscious, unrestrained rats, the intracerebroventricular injection of the cholinergic agonist, carbachol, or angiotensin II resulted in the transient stimulation of vasopressin secretion, elevation of mean arterial blood pressure, and reduction of heart rate. After the injection of carbachol (25 ng) into a lateral cerebral ventricle, the plasma vasopressin concentration in male rats was increased to twice that of female rats in each phase of the estrous cycle; mean arterial blood pressure was elevated more in males than females, whereas heart rate fell to the same extent in both sexes. In contrast, the increase in the plasma vasopressin concentration of males after the injection of angiotensin II (20 ng) was one-half that of females, and the hypertensive and bradycardic responses were similar in both sexes. Phase of the female estrous cycle had no effect on the responses to either agent. These findings indicate that central cholinergic and angiotensinergic mechanisms controlling vasopressin release are influenced differently by gender. The role of the gonadal steroid hormones in these mechanisms remains to be determined.

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