Dietary Regulation of Pancreatic Enzyme Synthesis, Secretion and Inactivation in the Rat

Abstract

Dietary regulation of the synthesis, secretion and inactivation of trypsin, chymotrypsin and amylase was studied in rats fed a nitrogen-free ration or diets containing casein, whole-egg protein or hydrolysates of these proteins. Measurements of the enzyme content of the pancreas after an 11-hour fast showed that substitution of the nitrogen-free diet for the casein diet depressed synthesis of the 3 enzymes, whereas replacement with whole-egg protein usually increased synthesis of trypsinogen and chymotrypsinogen but not amylase. Relatively more of the amino acid supply of the pancreas was diverted to chymotrypsinogen and less to amylase when whole-egg protein was fed. The reverse was true when casein was given. Rats fed the nitrogen-free diet synthesized relatively more trypsinogen. With respect to trypsinogen and chymotrypsinogen, the secretory response elicited by hydrolyzed casein and hydrolyzed egg protein was similar to the one evoked by casein. However, hydrolyzed egg protein was not equivalent to whole-egg protein. Interpretation of these results is based on the premise that dietary protein regulates pancreatic enzyme synthesis, in part, through amino acid pool(s) in the pancreas. The observation that the nitrogenfree diet retarded the rate of inactivation of amylase more than did the protein or hydrolyzed protein diets may be related to a protective effect of starch which was included in the nitrogen-free diet.