PKC is known to be activated by pancreatic secretagogues such as CCK and carbachol and to participate along with calcium in amylase release. Four PKC isoforms, alpha, delta, epsilon, and zeta, have been identified in acinar cells, but which isoforms participate in amylase release are unknown. To identify the responsible isoforms, we used translocation assays, chemical inhibitors, and overexpression of individual isoforms and their dominant-negative variants by means of adenoviral vectors. CCK stimulation caused translocation of PKC-alpha, -delta, and -epsilon, but not -zeta from soluble to membrane fraction. CCK-induced amylase release was inhibited approximately 30% by GF109203X, a broad spectrum PKC inhibitor, and by rottlerin, a PKC-delta inhibitor, but not by Gö6976, a PKC-alpha inhibitor, at concentrations from 1 to 5 microM. Neither overexpression of wild-type or dominant-negative PKC-alpha affected CCK-induced amylase release. Overexpression of PKC-delta and -epsilon enhanced amylase release, whereas only dominant-negative PKC-delta inhibited amylase release by 25%. PKC-delta overexpression increased amylase release at all concentrations of CCK, but dominant-negative PKC-delta only inhibited the maximal concentration; both similarly affected carbachol and JMV-180-induced amylase release. Overexpression of both PKC-delta and its dominant-negative variant affected the late but not the early phase of amylase release. GF109203X totally blocked the enhancement of amylase release by PKC-delta but had no further effect in the presence of dominant-negative PKC-delta. These results indicate that PKC-delta is the PKC isoform involved with amylase secretion.