Different inhibitory effects of the newly developed CCK receptor antagonists FK480 and KSG-504 on pancreatic exocrine and endocrine secretion in the isolated perfused rat pancreas.

Cholecystokinin (CCK) receptor antagonists are shown to have therapeutic as well as preventive effects in some types of acute pancreatitis. However, there is a possibility that administration of CCK receptor antagonists with a high inhibitory potency on the endocrine pancreas to patients with acute pancreatitis exacerbates the associated glucose intolerance. In the present study we simultaneously examined the effects of the newly developed benzodiazepine derivative FK480 and proglumide-related antagonist KSG-504 on CCK octapeptide (CCK-8)-stimulated exocrine and endocrine function in the isolated perfused rat pancreas. FK480 and KSG-504 inhibited CCK-8-stimulated pancreatic juice flow, protein output, and insulin release in a dose-dependent manner. FK480 was approximately 10 times more potent than KSG-504 in inhibiting exocrine and endocrine secretion. Both antagonists inhibited CCK-8-stimulated insulin release more potently than exocrine secretion. FK480 caused a dose-dependent residual inhibition of exocrine secretion after its removal from the perfusate, whereas insulin release was only slightly impaired even at the highest dose. In contrast, termination of KSG-504 infusion resulted in an immediate increase in both exocrine and insulin responses without causing any residual inhibition. With regard to the residual inhibition, therefore, KSG-504 had no significant influences on exocrine and insulin release, whereas FK480 inhibited exocrine secretion more potently than insulin response. These results suggest that FK480 might become a useful therapeutic agent for pancreatitis with respect to its long-duration inhibitory effect on exocrine secretion and short-duration inhibitory effect on insulin release.