Carbachol activates protein kinase C in dispersed gastric chief cells

We used an 'in situ' kinase assay to examine agonist-induced protein kinase C. (PKC) activation in dispersed chief cells from guinea-pig stomach. Phorbol 12-myristate 13-acetate (PMA), a phorbol ester, and carbamoylcholine, a cholinergic agent, caused a 4- and 3-fold increase in pepsinogen secretion from dispersed chief cells respectively. Whereas PMA caused a rapid 3-fold increase in peptide kinase activity, carbachol caused a 15% increase in activity that was inhibited by the PKC inhibitor, CGP 41,251. Concentrations of carbamoylcholine and a Ca2+ ionophore that were sub-maximal for stimulation of pepsinogen secretion did not cause PKC activation. These results indicate that, in the absence of PKC activation, other mechanisms, most likely involving changes in cellular Ca2+, are sufficient to stimulate pepsinogen secretion. Nevertheless, carbamoylcholine stimulated maximal secretion of pepsinogen only at concentrations that also resulted in activation of PKC. Moreover, these data indicate that relatively small increases in PKC activity (5-10%) can stimulate pepsinogen secretion from dispersed chief cells.