Cation transport by gastric H+∶K+ ATPase

Abstract

A vesicular microsomal fraction isolated from hog fundic mucosa demonstrates the capacity to take up equal amounts of RB⁺ and Cl⁻. The amount of the Rb⁺ uptake is sensitive to the extravesicular osmolarity, and rate of uptake is sensitive to temperature.⁸⁶Rb⁺ efflux is dependent upon the cation composition of the diluting solution. ATP, but not β-γ methylene ATP, induces a reversible efflux of⁸⁶Rb⁺ from loaded vesicles, and this is dependent upon a functional K⁺-ATPase. The ATP induced efflux is not affected by CCCP (carbonyl cyanidem-chlorophenylhydrazone) or TCS (tetrachlorosalicylanilide) nor by lipid soluble ions or valinomycin. Nigericin inhibits the efflux by 40%. Uptake of the lipid soluble ion¹⁴C-SCN⁻ has been demonstrated and is enhanced by ATP only in the presence of valinomycin. The results are consistent with a neutral or isopotential exchange of H⁺ for Rb⁺ mediated by K⁺-ATPase.