We studied the effect of changing perfusion pressure on the excretory function of isolated perfused nonclipped kidneys from the two-kidney Goldblatt hypertensive rat (GHR). Kidneys were studied from newly hypertensive rats about 8 days after contralateral renal artery clipping [blood pressure (BP) 138 ± 4.3 mm Hg] and before onset of hypertension 3 days following surgery (BP 111 + 1.9 mm Hg). In addition, nonclipped kidneys from adrenalectomized Goldblatt rats were also examined approximately 9 days following surgery (BP 114 ± 4.7 mm Hg). Kidneys from sham-operated rats served as controls. We noted no differences in GFR in kidneys from newly hypertensive rats and sham controls above a perfusion pressure of 120 mm Hg. In response to increasing perfusing pressure, perfusate flow and fractional sodium excretion were significantly lower in newly hypertensive rats than in sham-operated controls. No differences in glomerular filtration rate, perfusate flow, or sodium excretion were noted in kidneys from sham-operated rats or Goldblatt rats 3 days following surgery. After clipping, adrenalectomized (ADX) Goldblatt rats had less of a rise in blood pressure than did rats with intact adrenal glands. No attenuation of natriuresis was noted in the ADX-clipped group in response to increasing perfusion pressure. Isolated perfused kidneys from ADX rats had greater sodium excretion at all levels of pressure than kidneys from rats with intact adrenal glands. Deoxycorticosterone acetate replacement returned sodium excretion to that approaching intact rats. We conclude that nonclipped kidneys of newly hypertensive Goldblatt rats exhibit blunted pressure natriuresis. Adrenalectomy prevented the attenuation of the pressure natriuresis. We conclude that attenuated pressure natriuresis seen early in the course of Goldblatt hypertension appears to be related in part to residual mineralocorticoid effects.
