Food, duodenal extracts, and enzyme secretion by the pancreas

Previous studies have reported that injection of duodenal extracts from rats fed different meals into the celiac artery of recipient rats elicited the secretion of related pancreatic enzymes. We have been unable to reproduce the enzyme-specific increases in the average output of particular enzymes that were observed but did find changes similar in direction, although not magnitude, to those reported previously. The outputs of amylase and trypsinogen were compared by plotting individual data points and performing a regression analysis on them. The injection of duodenal extracts from lactalbumin hydrolysate-fed rats led to trypsinogen secretion being favored over that of amylase and vice versa for extracts from rats fed a glucose meal. In addition, it was found that cholecystokinin-pancreozymin produced a dramatic nonparallel transport of these two enzymes with amylase secretion being augmented to a greater degree than trypsinogen secretion. The relation between their outputs was curvilinear, i.e., the amylase dominance of secretion became more pronounced as overall enzyme output (not dose of hormone) increased. Thus, this nonparallel secretion does not seem to be the results of a discontinuous switch in the character of enzyme secretion produced by the hormone but a graded effect reflecting the magnitude of the response.