Effect of angiotensin on renal function of the dog.

Angiotensin (5 ng/kg/min and 50 ng/kg/min) was infused directly into the left renal artery of anesthetized dogs in order to examine its effects on the renal func tion. Urinary volume, creatinine clearance (GFR), PAH-clearance (RPF) and electrolyte excretion were decreased by infusion of angiotensin in a small dose. On the other hand extreme reductions of urinary volume, GFR, RPF and electrolyte excretion were observed immediately after the beginning of angiotensin infusion in a large dose, and were followed by gradual increases in these parameters during the administration of angiotensin (tachyphylaxis). In four out of six cases, urinary volume and sodium excretion surpassed the control values with increased extraction fraction of sodium. These results suggested that angiotensin affected the renal function mainly through two mechanisms: Firstly, the vasoconstrictive action of angiotensin on the renovascular system causes decrease in urinary output, and secondly the. direct action on the tubular system causes natriuresis.