Angiotensin-mediated alterations in nephron function in Goldblatt hypertensive rats.

The present study was performed to evaluate superficial nephron responses of the nonclipped kidney to angiotensin I converting enzyme inhibitor (CEI) (SQ 20,881, 3 mg . kg-1 . h-1) in two-kidney, one-clip Goldblatt hypertensive (GH) rats. Late proximal and early distal tubule collections were obtained before and during CEI. Significant increases in glomerular filtration rate, urine flow, sodium excretion, proximal and distal tubule flow rates, and single nephron glomerular filtration rate (from 24.6 +/- 1.7 to 27.5 +/- 1.6 nl/min) occurred despite reductions in arterial blood pressure (from 160 +/- 5 to 137 +/- 6 mmHg) during CEI. Proximal tubule absolute and fractional reabsorption of fluid, chloride, and total solute decreased significantly. In the nephron segment between the two collection sites, there were increases in absolute but decreases in fractional reabsorption. At the distal tubule level, fractional reabsorption but not absolute reabsorption decreased significantly. Proximal and distal tubule hydrostatic pressures increased significantly while peritubular capillary pressure decreased slightly. Responses following inhibition of angiotensin II formation suggest that there exists an angiotensin II-mediated enhancement in tubular reabsorption in the nonclipped kidney of Goldblatt hypertensive rats.