Role of Ca super(++) in Stimulus-Secretion Coupling in the Gastric Oxyntic Cell: Effect of A23187

The effects of Ca super(++) ionophore A23187 on H super(+) secretion and histamine release were studied in the isolated gastric mucosa of the toad Bufo marinus). A23187 added from the mucosal side stimulated H super(+) secretion. At high concentrations, A23187 also caused histamine release. This histamine was not sufficient to explain the effects of A23187 on H super(+) secretion. Metiamide, only partially inhibited the effect of ionophore. There was summation and/or potentiation of effects between A23187 and histamine. The results are consistent with the hypothesis that Ca super(++) acts as a second messenger in stimulus-secretion coupling in the oxyntic cell. It is possible that Ca super(++) and cAMP may interact as parallel second messengers in the control of gastric H super(+) secretion.