L'échangeur Na +/H + des cellules eucaryotes : Propriétés biochimiques et pharmacologiques, rôle physiologique

Abstract

A membrane mechanism that catalyses the electroneutral exchange of Na+ for H+ has recently been characterized in a variety of eukaryotic cells. This exchanger is inhibited by amiloride, a potent diuretic drug. It has been implicated in a number of important physiological processes such as the regulation of the intracellular pH, the reabsorption of Na+ by the renal proximal tubule, the regulation of the cell volume and the fertilization of the sea urchin egg. The Na+/H+ exchanger seems able to mediate the action of growth factors. The biochemical and pharmacological properties of the Na+/H+ exchange system are reviewed. They are very similar in the different cell types that have been studied. Yet the Na+/H+ exchange system can fulfil different functions in different cell types depending i) on its properties of interaction with intracellular H+, ii) on the presence of other membrane structures that are involved in the maintenance of transmembrane Na+ and H+ gradients and iii) on the presence of extracellular messages that modify its catalytic properties and, among them, its interaction with internal H+.