Short-term inhibition of duodenal tryptic activity does not affect human pancreatic, biliary, or gastric function

Existence of feedback inhibition of pancreatic secretion by luminal pancreatic trypsin in humans is controversial. We examined the effect of duodenal tryptic activity on pancreatic, biliary, and gastric functions. In six healthy volunteers, gastric acid secretion and emptying and the secretion of pancreatic enzymes, bicarbonate, and bile acids into the duodenum were measured for 7 hr with a double-marker perfusion technique. Each experiment consisted of six test periods. The effects of the addition of active and inactive aprotinin to duodenal saline perfusion were determined during fasting and after administration of a saline test meal. We found that (1) aprotinin eliminated tryptic activity in the preprandial state and reduced it by more than 95% during meal periods; (2) compared to inactivated aprotinin, no differences in the outputs of bicarbonate, amylase, lipase, chymotrypsin, and bile acids occurred during preprandial or postprandial aprotinin periods; and (3) gastric acid secretion, emptying, and duodenogastric reflux were similar during aprotinin and inactivated-aprotinin perfusions. We conclude that short-term, almost complete reduction of intraduodenal tryptic activity does not alter exocrine pancreatic secretion or gastric function in the unstimulated state or in response to a moderate stimulation by a saline test meal. Therefore the importance of negative feedback control of pancreatic secretion by acute alteration of intraduodenal tryptic activity must be questioned in healthy humans.