Feedback regulation of pancreatic secretion

We review the mechanisms underlying the feedback regulation of pancreatic e nzyme secretion in response to a meal. Pancreatic enzyme secretion in anima ls is known to be regulated by a negative feedback mechanism mediated by in testinal proteases such as trypsin and chymotrypsin. The presence of these enzymes in the small intestine suppresses pancreatic enzyme secretion, wher eas their removal increases it. This mechanism has also been noted in human s. Two novel peptides have been proposed to account for the stimulation of pancreatic enzyme secretion seen in response to feeding of a trypsin inhibi tor; one present in rat pancreatic juice and the other spontaneously secret ed by the rat small intestine. In both cases, trypsin and trypsin inhibitor s do not interact directly with the luminal surface of the small intestine, but their actions are mediated by a trypsin-sensitive, cholecystokinin-rel easing peptide. This is an explanation for the well-known stimulation of pa ncreatic enzyme secretion seen in response to dietary protein intake.