Effect of angiotensin on renal function in the rat

Abstract

The effect of angiotensin on renal function has been re-examined in the rat, a species in which only a natriuretic response to this hormone has been demonstrated so far. In unanesthetized Na-loaded rats, infusion of angiotensin in doses of .00005-.005 [mu]g/kg per min always reduced urinary Na excretion for the duration of a 30-min infusion. Doses of .05 [mu]g/kg per min and above had a biphasic action, causing a transient reduction followed by a marked increase in sodium excretion. Small doses of angiotensin consistently reduced the urinary concentration of Na and increased that of Co57 -cyanocobalamin, a glomerular filtration marker. During short 7-min infusions of angiotensin, plasma Co57 -cyanocobalamin concentrations were found not to vary from control. Changes in excretion rate of Co57-cyanocobalamin were, therefore, used as a guide to changes in glomerular filtration rate. During such infusions sodium excretion was found to be reduced without a consistent reduction in Co57 -cyanocobalamin excretion, suggesting that small doses of angiotensin may directly facilitate tubular Na reabsorption.