ELECTROGENICITY OF THE FROG GASTRIC-MUCOSA PROTON PUMP BASED ON POLARIZATION RESPONSES IN THE PRESENCE OF H-SECRETION INHIBITORS()

Recently, we have shown that polarization of an electrogenic H+/K+-ATP ase pump located in the secretory (luminal) membrane of the frog gastr ic mucosa is the major factor contributing to the increase in open cir cuit potential difference (OCPD) induced by voltage clamping. While th is transmucosal polarization was not affected by removal of Cl- and Na + and minimally affected by increasing the K+ concentration to 79 mM i n 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 effec ts of three other inhibitors of H+ secretion were examined, namely, ci metidine (beta blocker), SCH 28080 (H+/K+-ATPase inhibitor) and SCN- ( non-specific inhibitor). While cimetidine and SCH 28080 markedly reduc ed the polarization induced by voltage clamp, SCN- affected the polari zation to a lesser extent. These data further support the electrogenic ity of the frog gastric mucosa proton pump and the lack of a direct ef fect of SCN- on the pump.