Atropine-nonsensitive feedback regulatory mechanism of rat pancreatic enzyme secretion in response to food protein intake.

The effect of atropine on pancreatic enzyme secretion in response to removal of intraluminal protease was investigated using rats with an indwelling bile-pancreatic cannula. Stimulation of pancreatic enzyme secretion by diversion of bile-pancreatic juice was blocked by intravenous atropine [100 micrograms/(kg X h)] injection. On the other hand, stimulation of pancreatic enzyme secretion by intraluminal infusion of soybean trypsin inhibitor (SBTI) was not blocked by atropine administration. These results suggest that the feedback response of pancreatic enzyme secretion after removal of the intraluminal protease is controlled by at least two different systems, an atropine-sensitive mechanism and an atropine-nonsensitive mechanism. We detected and purified a peptide from rat bile-pancreatic juice that enhanced pancreatic enzyme secretion when the peptide was infused into the proximal intestine. In the atropine-administered rat whose small intestine was deprived of protease after intraluminal washing with saline containing SBTI, intraluminal infusion of the purified peptide stimulated pancreatic enzyme secretion markedly. These findings suggest that the atropine-nonsensitive feedback response of pancreatic enzyme secretion is at least in part mediated by the peptide.