On chymotrypsinogen and trypsinogen biosynthesis by pancreas of rats fed on a starch-rich or a casein-rich diet

Abstract

Tissue and mRNA levels of trypsin and the two forms of pancreatic secretory trypsin inhibitor (PSTI) were determined in the pancreatic tissue of rats fed on either a protein-free diet or two high-protein diets (44% and 64% protein, respectively) for 10 days as compared with control rats fed on a standard diet (22% protein). Two distinct response patterns were obtained, depending on the animals' nutritional status after ingestion of the protein-free and high-protein diets. After administration of the protein-free diet (containing 81% carbohydrate), the levels of the two mRNAs encoding both forms of the secretory trypsin inhibitor and anionic trypsinogen I increased significantly (100%, 110%, and 110%, respectively), whereas no significant increase in both PSTI mRNA levels were observed after the ingestion of the high-protein diets as compared with the control rats. Under all three dietary conditions, a coordinated pattern of response was observed between the two forms of inhibitors and anionic trypsinogen I at both the tissue mRNA and protein levels. The existence of a parallel change in trypsin activity and secretory trypsin inhibitor activity on the one hand, and trypsin mRNA and inhibitor mRNAs on the other hand, suggests that indentical influences regulate the expression of trypsin and pancreatic secretory trypsin inhibitor genes in response to the dietary protein content.