Na+/H+ exchange mechanism in the basolateral membrane of the rat enterocyte

Basolateral membrane vesicles from rat jejunal enterocytes, especially purified of brush-border contamination, were used for Na+ uptake. The basolateral membrane vesicles are osmotically active and under our experimental conditions Na+ binding is much lower than transport. An outwardly directed proton gradient stimulates Na+ uptake at both 5 microM and 5 mM concentrations. The proton gradient effect can be inhibited completely by 2 mM amiloride and partially by either FCCP or NH4Cl (NH3 diffusion). Membrane potential effects can be excluded by having valinomycin plus K+ on both sides of the vesicles. These results suggest that there is an Na+/H+ exchanger in the basolateral membrane of rat enterocytes.