Absence of an Exaggerated Renal Response to Acute Salt Loading In Salt-Hypertensive Rats.

Abstract

Summary The response to a standard oral load of hypertonic saline was studied in two strains of rats with opposite genetic susceptibility to hypertension. Following ingestion of a chow containing 8% NaCl, the B.P. of the strain predisposed to hypertension rose to an average of 168 mm Hg, while that of the strain resistant to developing hypertension remained 114 mm Hg. Control animals of both strains ingesting a 0.38% NaCl chow remained nor mo tensive. The natriuretic and diuretic response was the same in hypertensive and normotensive rats on high salt, but a significant difference was observed between these animals and their controls on low salt in that the latter excreted more water and sodium. Reversal from a high salt to a low salt diet enhanced diuresis and natriuresis comparably in both hypertensive and normotensive rats. Evidence is summarized indicating that an exaggerated natriuresis after an acute salt load in the hypertensive rat is not constantly present, and it was proposed that the phenomenon might be related to altered tubular structure. Evidence from other workers indicates that ADH secretion is enhanced by a high salt diet and this may play a role in the response to a salt load in rats. The authors wish to thank Drs. S. M. Friedman, E. P. Radford, Jr., and G. Giebisch, for reviewing the penultimate manuscript of this paper and making significant contributions to its ultimate form. We are indebted to Lorraine Tassinari, Martha Heine, and George Leitl for expert technical assistance.