Na+ Transport in Hypertension

Abstract

Several different lines of argument lead to the conclusion that the Na+ ion is important in hypertension. These include dietary and epidemiological studies, studies on the isolated cells and tissues of hypertensive subjects, and the association of the genetic predisposition to hypertension with abnormalities of cellular Na+ handling. In isolated cells, the most convincing abnormalities have been shown in the Na+ pump, where there is also evidence of a circulating inhibitor of the pump in essential hypertension, although the nature of the agent is still uncertain. The genetic association between essential hypertension and Na+ transport is best represented by alterations in Na(+)-Li+ countertransport in hypertensive subjects and their near relatives, although interpretation is rendered more complex by the influence of nongenetic factors on this system. The demonstrated differences between hypertensive and nonhypertensive subjects in the cellular handling of Na+ have not been integrated into a totally convincing explanation of the ultimate mechanism of the condition. Attention has focused on the possible mechanisms whereby an increase in intracellular Na+ may increase the concentration of cytosolic Ca2+ in the vascular smooth muscle, which is presumed to be a necessary precondition to a chronically elevated peripheral vascular resistance.