Potassium load in spontaneously hypertensive rats. Effects on blood pressure, renin-angiotensin, aldosterone, and intracellular electrolytes

Abstract

To study the mechanisms by which K⁺ influences vascular tone in hypertension, spontaneously hypertensive and normotensive rats were examined during an oral K⁺ load. There was a marked decrease in blood pressure in spontaneously hypertensive but not in normotensive rats. Intraerythrocytic K⁺ concentration and activity increased in normotensive but not in spontaneously hypertensive rats. Intraerythrocytic Na⁺ concentration and activity declined in both strains, the decrease in Na⁺ activity being more prominent in spontaneously hypertensive rats (P2+ activity decreased in spontaneously hypertensive rats (P+ load, the plasma renin activity being suppressed. The basal levels of plasma aldosterone in spontaneously hypertensive rats exceeded those in normotensive rats. It is concluded that intraerythrocytic Ca²⁺, and to a lesser extent Na⁺, correlate best with the blood pressure changes. These ionic changes may be mediated by hormonal factors. The significance of the elevated plasma aldosterone levels has not yet been entirely clarified.