Vascular sodium pump: endothelial modulation and alterations in some pathological processes and aging

The vascular Na+ pump maintains intracellular ionic concentration and contr ols membrane potential. Its inhibition by cardiac glycosides enhances the i ntracellular Na+ concentration. This in turn activates the Na+-Ca2+ exchang e mechanism, which induces intracellular Ca2+ increase, membrane depolariza tion, and noradrenaline release from perivascular adrenergic nerve endings; mechanisms that promote vasoconstriction. This article reviews the relevan ce of the Na+ pump in vascular tone regulation and the modulation of its ac tivity by the endothelium, The endothelium negatively modulates the vasocon striction elicited by Na+ pump inhibition by the release of nitric oxide, a ccording to some authors, or an unknown factor, as suggested by others, The possible existence of endogenous digitalis-like factors is also reviewed, as is the involvement of the vascular Na+ pump in some cardiovascular disor ders and aging, (C) 1999 Elsevier Science Inc, FLU rights reserved.