THE ROLE OF INSULIN IN THE INTERACTION OF SECRETIN AND CHOLECYSTOKININ IN EXOCRINE SECRETION OF THE ISOLATED-PERFUSED RAT PANCREAS

To investigate the role of insulin in the potentiation effect of secre tin and cholecystokinin (CCK) on pancreatic exocrine secretion, the pa ncreas was isolated from rats and perfused with modified Krebs-Hensele it solution containing glucose at three concentrations. Intraarterial glucose at concentrations of 2.5, 10, and 25 mM produced modest but si gnificant increases in both the pancreatic flow rate and the amylase o utput in a concentration-dependent manner. The mixture of secretin and CCK at concentrations of 18.5 and 14 pM, respectively, added to the g lucose solutions augmented the pancreatic flow rate and amylase output in relation to the glucose concentration. In the streptozotocin-tnate d pancreas, the mixture of secretin and CCK failed to augment the panc reatic exocrine secretion unless exogenous insulin was added to the pe rfusate. Secretin markedly potentiated the CCK-induced amylase output when insulin was present in the circulation. However, CCK did not pote ntiate the secretin-induced flow rate even if insulin was present in t he circulation. Insulin did not affect the actions of secretin alone b ut it potentiated the actions of CCK alone in both the pancreatic flow rate and the amylase output, It is concluded from the above results t hat insulin intensifies the combined actions of secretin and CCK in pa ncreatic exocrine secretion by potentiating the CCK action. Furthermor e, in the presence of insulin, secretin is able to potentiate the panc reatic enzyme secretion stimulated by CCK.