[Characterization of cholecystokinin receptors in gastric chief cells--effect of CCK analogs and CCK receptor antagonists on chief cells]

In isolated guinea pig gastric chief cells, gastrin-I and cholecystokinin-hexapeptide (CCK-4) stimulated pepsinogen release. However, the efficacies of these two peptide were 51% of that observed with CCK-octapeptide (CCK8). CR1409 and L-364718, both of which are new CCK receptor antagonists in pancreatic acinar cells, also inhibited 10(-8) M CCK8-stimulated pepsinogen release with a half-maximal inhibitory concentration (IC50) observed at 3 x 10(-9) M, respectively. The dose response curve to CCK8 for pepsinogen release shifted to the right in the presence of CR1409 or L-364718. The IC50 of these two antagonists for the CCK8-stimulated increase in cytosolic Ca2+ concentration monitored by Fura-2 were equal to those for CCK8-stimulated pepsinogen release. By contrast, the IC50 of dibutyryl cyclic GMP, a well-known CCK receptor antagonist, for CCK8-stimulated pepsinogen release was less than that for CCK8-stimulated increase in cytosolic Ca2+ concentration. Results suggested that CCK receptors in gastric chief cells are unique and may be different from CCK receptors in other tissues previously reported.