Effect of potassium depletion on two-kidney, one-clip renovascular hypertension in the rat

Abstract

Effect of potassium depletion on two-kidney, one-clip renovascular hypertension in the rat. There is considerable controversy about the hemodynamic effect of potassium in hypertension. To determine if K depletion could alter the control of blood pressure, studies were performed in rats with 2-kidney, 1-clip renovascular hypertension (RVH) after 3 to 6 wks of severe and moderate K depletion. After application of a 0.23mm clip to the left renal artery, rats were placed on a K-replete (KR) (240 mEq/kg), a moderately K-depleted (KDM) (59 mEq/kg), or a severely K-depleted (KDS) (5 mEq/kg) diet. After 3 wks, mean arterial pressure (MAP) reached 154 ± 3 in KR but only 121 ± 2 in KDM (P < 0.01) and 106 ± 4mm Hg in KDS (P < 0.001). After 6 wks, MAP was 160 ± 8 in KR, but only 132 ± 5 in KDM (P < 0.01) and 129 ± mm Hg in KDS (P < 0.01). Plasma K at 3 wks was 4.1 ± .1 in KR, but only 3.5 ± .1 in KDM (P < 0.05) and 2.3 ± .1 mEq/liter in KDS (P < 0.001). This was associated with an 8% decrease in muscle K in KDM and a 16% decrease in muscle K in KDS. Although KDS animals did not grow during the 6 wks of study, KDM rats gained 60% as much weight at 3 wks, and, by 6 wks, weight gain was comparable in KDM (101 ± 9) and KR (110 ± 9 g) animals (P = NS). The protective effect of K depletion was mediated by a decrease in systemic vascular resistance (SVR); KR .692 ± .06 compared to KDM .278 ± .01 (P < 0.001) and KDS .287 ± .02mm Hg/ml · min-1 · kg-1 (P < 0.001). The decrease in SVR could not be attributed to a decrease in plasma volume, plasma catecholamines, or plasma renin activity. The pressor response to exogenous AII was reduced by 60% while the depressor response to saralasin was reduced by 80% in KDM.To determine if K depletion could reverse established hypertension, rats with RVH were continued on the KR diet or changed to the K-depleted diet. After 3 wks, systolic pressure was 161 ± 6 in KR but only 119 ± 4 in KDM, and 120 ± 5mm Hg in KDS (both K < 0.02). We conclude that K depletion prevents the development of RVH and reverses established RVH and that the protective effect of K depletion may be mediated by a decrease in AII vascular sensitivity