Rat pancreatic response to intestinal infusion of intact and hydrolyzed protein

The effect of partial exclusion of pancreatic juice from the intestine on the pancreatic response to intraduodenal infusion of casein, casein hydrolysate, and trypsin inhibitor was investigated in conscious rats with chronic pancreatic and biliary fistulas. In controls all pancreatic juice collected was returned to the intestine. In partial diversion groups only 10% of the pancreatic juice collected was returned during each collection period. All bile was returned. Partial diversion of pancreatic juice slightly increased the response to NaCl, had no effect on the incremental response to casein hydrolysate, but doubled the incremental protein and volume response to casein infusion. Trypsin inhibitor infusion did not stimulate pancreatic secretion in controls but greatly increased pancreatic protein and fluid secretion in rats with partial diversion of pancreatic juice. The results confirm that protein hydrolysates are weak stimulants of pancreatic secretion in the rat compared with intact proteins and support the view that intact proteins and trypsin inhibitors stimulate pancreatic secretion in the rat by a common mechanism, i.e., by reducing feedback inhibition from luminal pancreatic proteases.