Electrogenicity of the frog gastric mucosa proton pump based on polarization responses in the presence of H(+)-secretion inhibitors

Abstract

Recently, we have shown that polarization of an electrogenic H+/K(+)-ATPase pump located in the secretory (luminal) membrane of the frog gastric mucosa is the major factor contributing to the increase in open circuit potential difference (OCPD) induced by voltage clamping. While this transmucosal polarization was not affected by removal of Cl- and Na+ and minimally affected by increasing the K+ concentration to 79 mM in both nutrient and secretory solutions, it was markedly reduced by 10(-3) M famotidine (beta blocker) or 10(-4) M omeprazole (H+/K(+)-ATPase inhibitor) in the nutrient solution. In present experiments, the effects of three other inhibitors of H+ secretion were examined, namely, cimetidine (beta blocker), SCH 28,080 (H+/K(+)-ATPase inhibitor) and SCN- (non-specific inhibitor). While cimetidine and SCH 28,080 markedly reduced the polarization induced by voltage clamp, SCN- affected the polarization to a lesser extent. These data further support the electrogenicity of the frog gastric mucosa proton pump and the lack of a direct effect of SCN- on the pump.