Feedback regulation of pancreatic exocrine secretion in minipigs.

Background: The mechanism behind the possible feedback regulation of pancreatic exocrine secretion is not well understood. Methods: Thirteen minipigs were prepared with fistulas to the pancreatic duct and the duodenum. Peripheral venous blood was obtained for determination of secretin and cholecystokinin (CCK) levels. Four different experiments were performed: 1) diversion and reinfusion of pancreatic juice; 2) intraduodenal infusion of NaHCO3 solution, with the same volume, bicarbonate concentration, and osmolality as the collected pancreatic secretion, and reinfusion of pancreatic juice; 3) reinfusion of pancreatic secretion for 1 h before and 2 h after a meal; and 4) diversion of pancreatic secretion and intraduodenal infusion of NaHCO3 solutions before and after a meal. Results: Reinfusing pancreatic juice significantly decreased pancreatic juice volume and bicarbonate output and slightly decreased the level of secretin in plasma. Alternating infusions of substitute NaHCO3 and pancreatic juice did not change pancreatic output of bicarbonate and protein, nor did it change the CCK and secretin levels in plasma. Replacing pancreatic juice with intraduodenal NaHCO3 infusions during a meal did not significantly modify the pancreatic secretion of bicarbonate and protein or the hormonal levels in blood. Conclusions: A negative feedback regulation of pancreatic exocrine secretion is present in starved minipigs. Duodenal acidity and plasma levels of secretin seem to be of importance, whereas duodenal enzymatic activity and the level of CCK in plasma probably are not. A postprandial negative feedback regulation through duodenal enzymatic activity and release of CCK into blood could not be shown.