Biological activity of des-Asp1-,Ileu8-angiotensin II (Ileu8-angiotensin III) in man

Biological activity of ileu8-angiotensin III (AIIIA) was studied in man. In 5 normal men intravenous infusion of 200 ng/kg/min of AIIIA for 30 minutes from 0900 h had no effect on blood pressure (BP) but caused a decrease in plasma renin activity (PRA) and an increase in plasma aldosterone (PA). This dose did not inhibit pressor and steroidogenic actions of angiotensin II (AII) infused into the normal men at a rate of 20 ng/kg/min for 30 minutes. In 3 patients with Bartter's syndrome 260-1,200 ng/kg/ min of AIIIA infusion for 30 minutes from 0900 h had no effect on BP but caused decreases in PRA and PA. These results indicate that in man AIIIA has no pressor action and no antagonistic effect on pressor action of AII but has PRA-lowering and aldosterone-stimulating effects. Antagonistic effect of AIIIA on steroidogenic action of AII was also shown in patients with Bartter's syndrome but not in AII-treated normal men. This may be due to the difference of administered dose of AIIIA.