Renal and adrenal responses to [des-Asp1]angiotensin I in the dog

There is evidence for the endogenous generation of [des-Asp1]angiotensin II (AIII) from a nonapeptide precursor, [des-Asp1]angiotensin I ([des-Asp1]AI). In the present study, the effects of equipressor doses of exogeneously administered [des-Asp1]AI and AIII on renal function and plasma aldosterone concentration were compared. Intravenous infusion of [des-Asp1]AI (75 ng/kg min-1 for 40 min) decreased renin secretion, renal blood flow, creatinine clearance, and sodium and potassium excretion in dogs. Infusion of AIII at one-third of the rate of [des-Asp1]AI (25 ng/kg min-1) produced comparable decreases in these same parameters. Filtration fraction was increased with both peptides. Both peptides also increased plasma aldosterone concentration to the same extent. A bolus injection (5 mg i.v.) of the converting enzyme inhibitor SQ 20,881 completely reversed the mean arterial pressure and renal blood flow responses to [des-Asp1]AI, but did not alter these responses to AIII. These data are consistent with the concept that endogenous generation of AIII from [des-Asp1]AI can occur via the action of converting enzyme on this substance.