[Comparison of acid and pepsinogen secretion control by oxyntopeptic cell of amphibians]

Pepsinogen and HCl secretion in the amphibian stomach is performed by a single cell type, the oxyntopeptic cell. The distribution of pepsinogen in gastric mucosa of Bufo marinus is heterogeneous and higher concentrations are located in the fundus. Both secretions respond to the same secretagogues. Histamine induces the highest response for the two secretions. Carbachol alone, without the endogenous histamine component, has a small effect. Forskolin and 8Br-cAMP have a similar effect to histamine. The Ca2+ ionophore, A23187, and the diacylglycerol analogue, octanoylacylglycerol (OAG) have a small effect on both secretions as carbachol. Joint addition of histamine and carbachol, or forskolin and carbachol, or of OAG and 8Br-cAMP induce a potentiated response for the two secretions. Quantitative analysis of responses and study of the relationship between them during stimulation with histamine plus carbachol revealed a non parallel and uncoupled pattern of stimulation for acid and pepsinogen secretions.