Related Experiment Videos
Angiotensin II blockade before and after marked sodium depletion in patients with hypertension
Insights
Angiotensin II blockade with saralasin effectively lowered blood pressure in hypertensive patients, especially after sodium depletion. The blood pressure reduction strongly correlated with initial plasma renin activity levels.
Area of Science:
- Cardiovascular Medicine
- Nephrology
- Pharmacology
Background:
- Hypertension management remains a significant clinical challenge.
- The renin-angiotensin-aldosterone system plays a crucial role in blood pressure regulation.
- Understanding the efficacy of angiotensin II blockade in different hypertensive subtypes is important.
Purpose of the Study:
- To investigate the effects of angiotensin II blockade using saralasin in patients with unilateral renovascular, bilateral renovascular, and essential hypertension.
- To assess the impact of sodium depletion on saralasin's hypotensive effects.
- To determine the relationship between saralasin's effects and plasma renin activity.
Main Methods:
- Intravenous administration of saralasin, an angiotensin II antagonist.
- Measurements of blood pressure, plasma renin activity, effective renal plasma flow (ERPF), and glomerular filtration rate.
- Comparison of effects under normal sodium intake and after sodium depletion.
Main Results:
- Saralasin decreased mean blood pressure in renovascular hypertension groups and increased it in essential hypertension on normal sodium intake.
- After sodium depletion, saralasin significantly reduced blood pressure in all groups, correlating with initial plasma renin activity.
- Saralasin reduced ERPF in all subgroups, with the effect on glomerular filtration rate and filtration fraction varying with sodium status.
Conclusions:
- The hypotensive action of saralasin is closely linked to plasma renin activity, irrespective of hypertension etiology.
- Saralasin's effect on renal hemodynamics differs between normal sodium intake and sodium depletion states.
- The study highlights the role of the renin-angiotensin system in mediating blood pressure and renal function in hypertension.
Abstract:
1. Angiotensin II blockade before and after marked sodium depletion in patients with hypertension [unilateral renovascular (eight), bilateral renovascular (four) and essential (four)] was performed by intravenous administration of the angiotensin II antagonist Sar1-Ala8-angiotensin II (saralasin). 2. On normal sodium intake, saralasin decreased mean blood pressure by 8 mmHg in the unilateral renovascular group, by 6 mmHg in the bilateral renovascular group and increased it by 3 mmHg in the essential hypertensive group. After sodium depletion saralasin decreased mean blood pressure by 33 mmHg, 35 mmHg and 18 mmHg respectively. The saralasin-induced decrease in blood pressure significantly correlated with the log of the initial plasma renin activity. 3. Saralasin infusion decreased effective renal plasma flow (ERPF) in all three hypertension subgroups, both on normal sodium intake and after sodium depletion. Glomerular filtration rate decreased in direct relation to the hypotensive effect of saralasin but ERPF showed this relationship only after sodium depletion. On normal sodium intake saralasin increased filtration fraction by 17%, but decreased it by 7% after sodium depletion. 4. It is concluded that the hypotensive action of saralasin closely correlates with the value of circulating plasma renin activity, apparently independent of the aetiology of the hypertension. The decrease in ERPF during saralasin infusion in the patients on normal sodium intake seems mainly related to the agonistic activity of saralasin, but that after sodium depletion to the hypotensive effect of saralasin.