Angiotensin stimulated AVP-release in humans

Area of Science:

• Endocrinology
• Nephrology
• Physiology

Background:

• Previous studies in rats and dogs indicated a relationship between the renin-angiotensin-aldosterone system (RAAS) and arginine vasopressin (AVP) secretion.
• The RAAS regulates salt balance, while AVP controls water balance, suggesting a potential interplay between these systems.

Purpose of the Study:

• To investigate the relationship between angiotensin II (A-II) and arginine vasopressin (AVP) in humans.
• To determine if A-II infusion stimulates AVP release in humans, similar to findings in animal models.

Main Methods:

• Development of a sensitive double antibody radioimmunoassay for measuring plasma AVP levels.
• Infusion of A-II in recumbent human subjects at a concentration of 3-30 ng/min-kg.
• Monitoring of plasma AVP levels, blood pressure, plasma renin activity, serum osmolality, and serum sodium concentration before, during, and after A-II infusion.

Main Results:

• Basal plasma AVP levels were 3.4 ± 2.2 pg/ml.
• A-II infusion led to a 2-5 fold increase in plasma AVP levels within 30 minutes, returning to baseline within 90 minutes.
• A-II infusion caused a 20 mm Hg rise in blood pressure and a decrease in plasma renin activity, without altering serum osmolality or sodium concentration.
• Norepinephrine infusion did not affect plasma AVP levels, ruling out a non-specific blood pressure effect.

Conclusions:

• Angiotensin II directly stimulates the release of arginine vasopressin in humans.
• This study establishes a functional link between the salt-regulating RAAS and the water-regulating AVP system in humans.
• The findings support the hypothesis that the RAAS and AVP system interact to maintain fluid and electrolyte homeostasis.