Renal Responses to Angiotensin II and 1-sar-8-ala-aII in Sodium Replete and Deplete Dogs

In order to elucidate the effects of angiotensin II on renal function, angiotensin II (AII; 1 ng/kg per min) and the AII antagonist 1-sar-8-ala-angiotensin II (AIIA; 200 ng/kg per min) were infused into the renal artery of anesthetized dogs (pentobarbital), on either a high (8 mmol/kg per day for seven days) or a low sodium intake (0.5 mmol/kg). In sodium replete dogs AII produced renal vasoconstriction with decreased RBF (-28%; P less than 0.001), but with less decrease of GFR (-14%; P less than 0.001), leading to an increase of FF (+19%, P less than 0.001), andantidiuresis (-39%, P less than 0.001); the antinatriuresis (-58%; P less than 0.001) exceeded the antidiuresis (P less than 0.001). delatRBF (-10%; P less than 0.001) was less pronounced (P less than 0.001) during AII in sodium deplete dogs, GFR remained unchanged, but FF increased to the same extent (+16%; P less than 0.05); diuresis and urinary electrolyte excretion were however not affected. AIIA did not affect RBF, GFR, FF, nor diuresis in sodium replete dogs suggesting that endogenous AII has no tonic influence on renal function in these conditions. In sodium deplete animals AIIA produced an 11% (P less than 0.001) increase of RBF, without changes of GFR; FF decreased by 12% (P less than 0.01), but diuresis, natriuresis and kaliuresis were not affected.