Renal Pressure-Flow Relationships in Severely Hypertensive Rabbits 1

Abstract

Abstract

The relationship between renal perfusion pressure and renal blood flow (RBF) was studied in the contralateral or not-clipped kidneys of seven two-kidney one-clip renovascular severely hypertensive rabbits and in the right kidneys of eight normotensive rabbits. Thirty to forty days after clipping the left renal artery, severely hypertensive rabbits were characterized by blood pressures significantly greater than normotensive (105 vs 80 mm Hg), and plasma renin activities three times greater than in normotensive rabbits. The absolute RBF to the right kidney was greater in hypertensive rabbits, but these kidneys were hypertrophied so that renal blood flow per gram kidney weight was the same (2.4 ml/min) in kidneys of both hypertensive and normotensive rabbits. Sequentially reducing renal perfusion pressure decreased RBF similarly in both groups suggesting hypertensive rabbits required 27% greater perfusion pressure to achieve RBF similar to that of normotensive rabbits. When the competitive angiotensin antagonist [Sar¹-Ile⁸]-angiotensin II was administered to both groups, there was no significant change in the RBF of normotensives. In the hypertensive rabbits, however, blood pressure dropped to a value not different from normotensive while renal vascular resistance decreased such that RBF was maintained at a normal level. These results suggest the contralateral kidneys of severely hypertensive rabbits chronically adapt RBF to normal levels despite elevated renal perfusion pressure.