Interactions between bile and pancreatic juice diversions on cholecystokinin release and pancreas in conscious rats

Pancreatic exocrine secretion in the conscious rat is regulated by proteases secreted by the pancreas, and cholecystokinin (CCK) is known to be involved in its mechanism. It has also been reported that the absence of either pancreatic juice or bile in the duodenum could stimulate pancreatic secretion. Therefore, differences in CCK release responding to the exclusion of bile, pancreatic juice (PJ), or both bile and pancreatic juice (BPJ) from the intestine were examined by using a bioassay for cholecystokinin. Plasma CCK levels were increased by all three treatments compared with the basal value, the order of their effects being BPJ greater than PJ greater than bile diversion, and CCK concentrations produced by BPJ diversion were much greater than can be explained as simply summed effect of exclusions of bile and PJ. Pancreatic exocrine secretions were significantly increased by PJ and BPJ diversions, but the effect of bile diversion on the pancreas was not statistically significant. An additional infusion of CR-1409 (0.1 mg/rat), one of CCK receptor antagonists, inhibited exocrine function stimulated by BPJ diversion. We conclude (i) BPJ diversion is the strongest endogenous stimulant on CCK release; (ii) the potentiation between bile and PJ diversions is induced on CCK release; (iii) pancreatic protein secretion during BPJ diversion is mainly modulated by CCK.