RENAL RESPONSES TO SLIGHT ELEVATIONS OF RENAL ARTERIAL PLASMA ANGIOTENSIN II CONCENTRATION IN DOGS

1. Angiotensin II was infused into the renal artery of intact kidneys of slightly volume expanded anaesthetized dogs at rates of 125, 250, 500, and 1000 pg/kg body weight per min, resulting in elevations of the calculated renal arterial plasma angiotensin II concentration of 16·9 (s.e.m. = 2·1), 35·0 (s.e.m. = 4·3), 73·3 (s.e.m. = 8·8), and 159·8 (s.e.m. = 20·4) pg/ml. 2. Angiotensin II caused significant dose-dependent decreases of renal blood flow and of renal plasma flow of -4·1% (s.e.m. = 1·5, P(0·05) at the lowest and of -19·6% (s.e.m. = 1·4, P(0·001) at the highest rate of infusion. Glomerular filtration rate remained essentially unchanged at the two lower infusion levels and decreased by -6·7% (s.e.m. = 2·2, P(0·05) and -8·3% (s.e.m. = 2·5, P(0·05) at the higher rates of infusion. Filtration fraction thus increased by +6·3% (s.e.m. = 2·4, P(0·05) at the lowest and by +14·2% (s.e.m. = 3·6, P(0·01) at the highest rate of infusion. 3. Urine volume decreased by -7·7% (s.e.m. = 0·8, P(0·001) at the lowest and by -35·2% (s.e.m. = 4·8, P(0·001) at the highest rate of infusion, while the study showed similar dose-dependent decreases for urinary sodium and potassium excretion and for the fraction of filtered sodium excreted.