Electrical and molecular coupling between sodium and proton fluxes in basolateral membrane vesicles of rat liver

Mechanisms of Na⁺–H⁺ exchange in the hepatocyte were studied utilizing isolated basolateral membrane vesicles prepared by two different methods: Evidence was obtained for the existence of molecular coupling of Na⁺ and H⁺ fluxes (Na⁺/H⁺-antiport) which exhibits saturation kinetics (Km 7 mmol/l Na⁺) and is inhibited by amiloride (1.0 mmol/l). Although the two membrane preparations showed differences with respect to ionic permeabilities, our data suggest that a relatively high H⁺ conductance exists in the basolateral plasma membrane. Hence, electrical coupling of conductive H⁺ and Na⁺ fluxes in the opposite direction could contribute to net Na⁺–H⁺ exchange across the basolateral hepatocyte plasma membrane.