SUMMARYThe influence of the renln-angiotensin system on individual kidney function of two-kidney, one clip Goldblatt hypertensive (GH) rats was evaluated by determining renal functional responses during intravenous infusion of converting enzyme inhibitor (CEI) (SQ 20,881, 0 J rag/100 g-hr) for 3.5 bourn. Rats were made hypertensive by placing a 0.25 mm silver clip on the right renal artery 3-4 weeks prior to study. Normal rats and GH rats were prepared to allow urine collections from each kidney. Mean arterial pressure of GH rats fell significantly from preinfusion levels of 153 ± 7 to 126 ± 4 mm Hg during CEI infusion. Despite this decrease in arterial pressure, the nondipped kidneys with reduced renal renin activity (14 ± 5 vs 293 ± 40 ng Al/mg-hr in the clipped kidney) exhibited dramatic increases in gtomerular filtration rate (GFR) (from 1.45 ± 0.06 to 2.56 ± 0.35 ml/mln), urine flow (4.82 ± 0.71 to 9.11 ± 1.19 ^il/mln), sodium excretion (0.10 ± 0.02 to 1.15 ± 0.39 M Eq/mln), fractional sodium excretion (0.05% ± 0.02% to 0.43% ± 0.18%), and potassium excretion (0.94 ± 0.08 to 2.50 ± 0.55 /