H(+)-K(+)-ATPase contributes to regulation of pHi in frog oxynticopeptic cells

The effect of intracellular acidosis on luminal H+ secretion and the role of H(+)-K(+)-ATPase in regulation of intracellular pH (pHi) in oxynticopeptic cells (OPC) (measured with a pH-sensitive fluorescent dye) were examined in intact sheets of in vitro frog (Rana catesbeiana) gastric mucosa. Intracellular acidosis of OPC induced by decreasing pH in the serosal solution (pHs) from 7.2 to 6.0 reversibly increased forskolin-stimulated H+ secretion without increasing endogenous histamine release. The observed increase in H+ secretion was unaffected by either 1 mM cimetidine or 1 mM histamine, but was accentuated by 1 mM amiloride, an effect abolished by 0.3 mM omeprazole. Steady-state pHi values in stimulated or resting OPC at pHs 7.2 were not significantly different. However, pHi in OPC was significantly higher in stimulated than in resting tissues at pHs 6.9, a difference accentuated by decreasing pHs to 6.4 or by 1 mM amiloride. Amiloride completely prevented recovery from intracellular acidosis induced by pHs 6.4 or 6.9 in omeprazole-treated tissues, but only partially mitigated recovery in cimetidine- or forskolin-treated tissues. At pHs 6.4, high luminal [K+] (100 mM) increased H+ secretion and hastened recovery of pHi in cimetidine-treated tissues in the presence of amiloride. These results suggest that, in intact sheets of in vitro frog gastric mucosa, 1) intracellular acidosis stimulates luminal H+ secretion via histamine-independent mechanisms and 2) H(+)-K(+)-ATPase contributes to the recovery of OPC from intracellular acidosis.