On the mechanism of stimulation of H super(+) transport in gastric mucosa by Ca super(++) ionophore A23187. II. Ca super(++)-cyclic AMP interactions

The possibility of interactions between calcium and cyclic AMP (cAMP) in the mechanism of stimulation of H super(+) transport by A23187 was studied in the isolated gastric mucosa of the toad Bufo marinus). A23187 stimulated H super(+) secretion and histamine release. The amount of histamine released by A23187 did not explain the degree of stimulation. Ca super(++) ionophore produced an overstimulation of secretion after H super(+) transport had been induced by supramaximal effective concentrations of histamine (10 super(-4) M). In the presence of metiamide, IMX potentiated the response to A23187. The results are consistent with an interaction between Ca super(++) and ionophore-released histamine at the oxyntic cell in the stimulation by A23187. The stimulatory response may be the result of a potentiation between calcium and cAMP at the intracellular level.