Effect of adrenal arterial infusion of P-113 on aldosterone secretion in Na-deficient sheep.

To examine the role of the renin-angiotensin system in aldosterone regulation, P-113 ([Sar1,Ala8]angiotensin II) was infused into the arterial blood supply of the transplanted adrenal gland in conscious sheep. Effects on the aldosterone response to infused angiotensin II and III in sodium-replete sheep were compared with effects of P-113 on aldosterone secretion in sodium deficiency. P-113 infusion up to 1,000 microgram/h for 1-2 h did not consistently alter aldosterone secretion in sodium-deficient sheep. However, in sodium-replete sheep P-113 infusion for 20 min at 10 microgram/h or more abolished aldosterone responses to high blood levels of angiotensin II and III produced by systemic intravenous or adrenal intra-arterial infusion. P-113 infusions alone had minor agonist activity on aldosterone secretion in sodium-replete sheep. These results indicate that the increased secretion of aldosterone in Na-depleted sheep is not simply and commensurately determined by increase of angiotensin II and III concentration in the arterial blood perfusing the adrenal gland.