Renal hemodynamics and sodium excretion in stroke-prone spontaneously hypertensive rats.

Renal blood flow (RBF), renal vascular resistance (RVR), glomerular filtration rate (GFR), and sodium and water excretion were measured in anesthetized stroke-prone spontaneously hypertensive rats (SHRSP), spontaneously hypertensive rats (SHR), and control Wistar-Kyoto rats (WKY) at 9 wk of age. Mean arterial pressure in SHRSP and SHR was significantly higher than that in WKY. RBF was slightly increased in SHR and decreased in SHRSP. RVR was markedly elevated only in SHRSP. In both strains of SHR, GFR was significantly increased but water and sodium excretion were similar. When renal perfusion pressure in both strains of SHR was reduced to a level similar to that of WKY by aortic constriction, RBF was slightly but significantly reduced in both SHRSP and SHR, and GFR only in SHRSP. RVR in SHRSP was still higher. Sodium and water excretion were markedly decreased in both SHR and SHRSP. The data suggest that SHRSP are characterized by an alteration in renal hemodynamics at a young age and support the hypothesis that kidneys of SHR require a higher arterial pressure than kidneys of WKY to excrete a given amount of salt and water.