[Trigger function of cyclic AMP in the initiation of HCl secretion by the frog gastric mucosa]

Histamine (0.3 mM) caused a rapid but transient increase in cAMP level prior to a rise in HCl secretion in the isolated gastric mucosa of frog Rana esculenta. H2-receptor blocking agent cimetidine (0.01 mM) suppressed HCl secretion which had been preceded by a decrease in cAMP level. No statistically significant changes in cGMP content were found. Dibutyryl cAMP imitated the effect of histamine. In frogs captured in spring, with a high level of HCl secretion and high content of cAMP, histamine exerted no stimulating effect. It seems to be the cAMP and not cGMP that acts either as a trigger in activation of HCl secretion or as a stabilizer of induced secretion.