Effect of adrenal arterial infusion of saralasin (P113) on aldosterone secretion.

To test the role of the renin/angiotensin system in aldosterone regulation, Sar1-Ala8-angiotensin II (P113) was infused into the arterial blood supply of transplanted adrenal glands in conscious sheep. Effects on the aldosterone response to infused angiotensin II and III in sodium replete sheep were compared with effects in sodium deficiency. Adrenal arterial infusion of P113 up to 1,000 mug/h for 1-2h did not consistently alter the high aldosterone secretion rates of sodium-deficient sheep. However, infusion of P113 at 10 mug/h or more abolished aldosterone responses to angiotensin II infusion that caused high physiological blood levels of angiotensin II. These results are against the proposal of a primary proportional causal relationship between blood angiotensin II concentration and aldosterone secretion rate in sodium deficiency. They are also against the possibility that such a primary role is played by blood-borne angiotensin III.