Captopril attenuates diuretic and natriuretic actions of furosemide but not atrial natriuretic peptide.

Atrial Natriuretic Peptide (ANP) exerts a potent diuretic and natriuretic action in rat, dog and man. To test whether these actions of ANP are due to antagonism of the antinatriuretic actions of endogenous angiotensin II, an examination was made of the renal actions of ANP in anesthetized rats with and without captopril pretreatment. Captopril treatment did not alter the diuretic and natriuretic action of a single, intravenous bolus injection of ANP (1000 ng of the 8-33 ANP). Captopril treatment did significantly attenuate the diuretic and natriuretic actions of Furosemide (20 mg/kg ip). This attenuation was not reversed by concomitant, exogenous angiotensin II infusion. These results suggest that while ANP exerts its renal actions independently of the circulating renin-angiotensin system the diuretic and natriuretic action of Furosemide is modulated by a substrate of angiotensin converting enzyme.