The inhibitory effect of CR-1409 on amylase secretion and intracellular Ca2+ mobilization in rat pancreatic acini in vitro

The inhibitory effects of CR-1409, a new glutaramic acid derivative developed as a cholecystokinin (CCK) receptor antagonist, on caerulein-stimulated amylase secretion and on intracellular Ca2+ ([Ca2+]i) mobilization were studied in isolated rat pancreatic acini. Pancreatic acini were prepared by collagenase digestion method and loaded with 1μM fura-2/AM for measurement of the intracellular free Ca2+ concentration. Amylase release was examined by a perifusion method. Stimulation with 10-10M caerulein, 10-5M carbachol, or 10-8M gastrin-releasing peptide (GRP) led to biphasic amylase release and increase in [Ca2+]i. CR-1409 at 1 and 5μM inhibited, by 50 and 84%, respectively, the amylase secretion and increase in [Ca2+]i induced by 10-10M caerulein, and 25μM CR-1409 completely inhibited both amylase secretion and increase in [Ca2+]i induced by caerulein. However, 25μM CR-1409 did not inhibit unstimulated secretion of amylase or the secretions induced by carbachol and GRP, which are also mediated by changes in intracellular Ca2+. We conclude that CR-1409 acts as a specific inhibitor of the CCK receptor in the pancreas, and is useful in studies on the involvement of the release and action of CCK in vitro.