THE DIRECT RENAL TUBULAR EFFECT OF ANGIOTENSIN-II IN CHICKEN

Taking advantage of the particular renal vascular arrangement in cocks , angiotensin II was injected (0.12-0.96 mu g/min) into the portal sys tem of one kidney in order to increase the angiotensin-II concentratio n in the physiological nanomolar range at the level. of the renal tubu les. Angiotensin II induced an increase in blood pressure of 5% and a bilateral rise in glomerular filtration rate and effective renal plasm a now of 28 and 22%, respectively. The urine volume increased five tim es on the infused side and three times on the control side. The Na+ ex cretion increased 14 times on the infused side and only seven times on the control side. During angiotensin infusion, the fractional water e xcretion was 4.9% on the infused side and 2.9% on th e control side ve rsus 1.1 and 1.2% during the control period. For the fractional Na+ ex cretion, the respective values were 2 and 1.2% versus 0.2 and 0.2% dur ing the control period. The differences between the two kidneys demons trate the direct tubular action of angiotensin II, inhibiting the tubu lar Na+ and water reabsorption at physiological nanomolar concentratio ns. Angiotensin seems thus to play an important intrarenal role.