Effects of SQ 20,881 on the intact kidney of dogs with two-kidney, one clip hypertension.

SUMMARY It has been suggested that in two-kidney, one clip hypertension, the undamped kidney (UK) actively contributes to hypertension by reducing its excretory ability in response to increased levels of Circulating angiotensin II. By exteriorizing the ureter to the dog's flank several weeks beforehand, we measured renal function directly from the UK of six chrogic renal hypertensive (> 3 weeks) and six normal dogs (ND). Mean blood pressure (indwelling catheter) and renal function were measured in the trained dogs for two 20- minute periods before and during a 40-rainute intravenous infusion of SQ 20,881, at a dose (300 Mg/kg + 3 Mg/kg/min) that caused no changes in blood pressure (BP). In dogs with chronic renal hypertension [121 mm Hg ± 2 SE] and mild elevation of plasma renin activity (2.0 ± 0.4 vs 0.4 ± 0.1 ng/ml/hr in ND), infusion of SQ 20,881 caused marked increases in sodium excretion (UNaV), glomerular filtration rate, and effective renal plasma flow. Moreover, the changes in UNaV and effective renal plasma flow were highly correlated (r = 0.77, p < 0.001). In normotensive dogs (99 ± 2 mm Hg) SQ 20,881 caused a 30% ± 5% rise in UNaV, a modest increase in glomerular filtration rate (4% ± 2%) and no change in effective renal plasma floVr. Infusion of a mild pressor dose of angiotensin II (4 ng/kg/min) produced decreases in sodium excretion, effective renal plasma flow, and glomerular filtration rate in the normotensive dogs. In the hypertensive animals, the same infusion rate of angiotensin II caused significant natriuresis without changes in effective renal plasma flow and glomerular filtration rate. These results suggest that the mild increases in plasma renin activity associated with the chronic phaseof two-kidney, one clip hypertension contribute in modifying the renal function of the untouched kidney.