Adaptive response of the rat pancreas to dietary substrates : Parallel regulation of trypsinogen and pancreatic secretory trypsin inhibitor

Chronic pancreatitis has been associated with malnutrition in alcoholic patients and malnourished juveniles. The composition of the diet, especially the protein content, regulates the synthesis of secretory proteins in the rat pancreas. Adaptive responses of the pancreas have shown that anionic proteases (e.g., trypsinogen) are upregulated during protein deprivation. We hypothesize that the (cationic) pancreatic secretory trypsin inhibitor (PSTI) is down-regulated after a protein-deficient diet. Low PSTI levels might cause a lack of protection from prematurely activated trypsin and therefore enhance the risk for pancreatic inflammation. Over a period of 1 month, rats were fed one of four isocaloric diets with a casein content varying from 0 to 82%. PSTI and trypsinogen mRNA remained fairly constant, irrespective of the diet composition. Trypsinogen and elastase secreted into pancreatic juice were upregulated after a protein-deficient diet relative to a control diet. Contrary to our hypothesis, PSTI was also upregulated. Parallel secretion of trypsinogen and PSTI appears to ensure protection against premature activation even under extreme dietary conditions.