Feedback regulation of exocrine pancreatic secretion in dogs.

Important basic physiological mechanisms of exocrine pancreas secretion were delineated in a canine model. However, dogs have been considered unsuitable for the study of the controversial feedback regulation of exocrine pancreas secretion. The present study reveals a marked modification of pancreas secretion following the intraduodenal instillation of lipase: The postprandial lipase secretion decreases from 2,421 U x 180 min-1 to 1,490 U x 180 min-1, but simultaneously determined cholecystokinin (CCK) concentrations in plasma do not increase under these circumstances. The intraduodenal application of a protease inhibitor (800 mg camostate) significantly stimulates the secretion of the exocrine pancreas in the fasting dog: After 15 min the protein release increased to 133 +/- 30 mg. Intravenous atropine blocks this increase. The plasma concentrations of CCK are not significantly influenced. These results in our canine model show that the secretory activity of the exocrine pancreas depends on the intraduodenal enzyme content. CCK is irrelevant in this context.