THE DIRECT RENAL TUBULAR EFFECT OF ANGIOTENSIN-II IN CHICKEN

Abstract

Taking advantage of the particular renal vascular arrangement in cocks, angiotensin II was injected (0.12-0.96 mu g/min) into the portal system of one kidney in order to increase the angiotensin-II concentration in the physiological nanomolar range at the level. of the renal tubules. Angiotensin II induced an increase in blood pressure of 5% and a bilateral rise in glomerular filtration rate and effective renal plasma now of 28 and 22%, respectively. The urine volume increased five times on the infused side and three times on the control side. The Na+ excretion increased 14 times on the infused side and only seven times on the control side. During angiotensin infusion, the fractional water excretion was 4.9% on the infused side and 2.9% on th e control side versus 1.1 and 1.2% during the control period. For the fractional Na+ excretion, the respective values were 2 and 1.2% versus 0.2 and 0.2% during the control period. The differences between the two kidneys demonstrate the direct tubular action of angiotensin II, inhibiting the tubular Na+ and water reabsorption at physiological nanomolar concentrations. Angiotensin seems thus to play an important intrarenal role.