EFFECTS OF ATRIAL-NATRIURETIC-PEPTIDE ON ANGIOTENSIN-II-INDUCED ANTINATRIURESIS IN ANESTHETIZED DOGS

Inhibitory effects of atrial natriuretic peptide (ANP) on angiotensin II (ANG II)-induced renal responses were examined in anesthetized dogs . ANG II (5 ng/kg per min) was infused intravenously and changes in re nal hemodynamics and urine formation were compared between the ANP (10 ng/kg per min)-infused kidney and the contralateral vehicle-infused ( control) kidney. ANG II reduced absolute and fractional urinary sodium excretion in both the ANP-infused kidney and the control kidney. ANG II also reduced glomerular filtration rate in the control kidney but n ot in the ANP-infused kidney. The ANG II-induced reduction in urinary sodium excretion in the ANP-infused kidney was smaller than the respon se in the control kidney, whereas ANP did not affect the reduction in fractional sodium excretion. These results suggest that ANP prevents h ypofiltration and thereby attenuates the antinatriuresis induced by AN G II.