Vasoactive effects of potassium in kidneys of hypertensive rats fed a high-potassium diet

Design and methods Levels of dietary and serum potassium are thought to cor relate inversely with vascular resistance and blood pressure, This study ex amined renal vascular resistance in perfused rat kidneys partially preconst ricted with 10 mu mol/l phenylephrine, quantifying changes in the resistanc e when levels of potassium in the perfusate ([K+](o)) were varied between 2 and 80 mmol/l, Results In kidneys from 17-week-old Wistar-Kyoto rats (WKY strain) fed a no rmal diet (American Institute of Nutrition AIN-76 diet), the resistance dec reased when [K+](o) was raised from 4 to 6-20 mmol/l, whereas resistance in creased when [K+](o) was either lowered to 2 mmol/l or raised above 25 mmol /l. The vasodilation that occurred at 13 mmol/l [K+](o) was blocked by 100 mu mol/l BaCl2 and 10 mu mol/l ouabain in an additive manner, suggesting th at both the inward rectifier K+ channel and the Na-K-ATPase underlie the di lation, Kidneys from spontaneously hypertensive rats (SHR strain) fed the A IN-76 diet displayed modestly enhanced vasodilations and vasoconstrictions as compared to WKY, A high-potassium diet (AIN-76 supplemented with 3.5% po tassium citrate, provided for 8 weeks) led to exaggerated vasoconstrictive effects of [K+](o), and modestly enhanced vasodilations, in WKY rats. In co ntrast, the diet led to attenuated vasoconstrictions, and dramatically enha nced vasodilations, in the SHR strain. The diet did not affect the blood pr essure increase or weight gain of either strain. Conclusions Changes in the responsiveness of blood vessels to extracellular potassium might underlie some beneficial effects of high-potassium diets i n hypertensive individuals, J Hypertens 1999, 17:1481-1488 (C) Lippincott W illiams & Wilkins.