FUNCTIONAL COUPLING BETWEEN THE CYCLIC ADENOSINE-MONOPHOSPHATE PATHWAY AND CHOLECYSTOKININ SECRETION IN RIN CELLS

The cellular events associated with cAMP-dependent cholecystokinin (CCK) release were investigated with an X-ray induced rat pancreatic tumor cell line (RIN 1056 E). Forskolin dose-dependently stimulated the release of CCK. Agents that increase [Ca2(+)](i) (thapsigargin, Bay K 8644, ionomycin) also stimulated the release of CCK. Conversely, absence of extracellular Ca2+ or cell treatment with various calcium channel blockers strongly reduced the forskolin-induced CCK release. Finally, the cAMP-kinase inhibitor H89, the calmodulin antagonist W7 and the Ca/calmodulin-dependent protein-kinase II inhibitor KN62 strongly inhibited the forskolin-evoked CCK secretion. We conclude that the release of CCK via a cAMP-dependent pathway is dependent on the activation of voltage-dependent calcium channels and may implicate protein kinase A, calmodulin and the Ca/calmodulin-dependent protein kinase II. (C) 1994 Academic Press, Inc.