Dietary regulation of pancreatic protein synthesis. I. Rapid and specific modulation of enzyme synthesis by changes in dietary composition.

Dietary adaptation of pancreatic protein synthesis and of pancreatic enzyme concentration, was studied over the first 24 h of exposure to a new diet. Rats were adapted to a carbohydrate-rich (G) or to a protein-rich diet (P) and were switched to the opposite regime after a 15 h fast. The evolution of the relative rate of synthesis of amylase, chymotrypsinogen and trypsinogen and of the pancreatic concentration of amylase and chymotrypsinogen were followed. Fasting caused important modifications in the relative rate of synthesis of the three enzymes in rats adapted to a P diet. Adaptative changes in the relative rate of synthesis of amylase, chymotrypsinogen and trypsinogen were seen within 2 h after the beginning of refeeding. These changes were followed by corresponding adaptative modifications in pancreatic contents 4 h after the beginning of refeeding. After 24 h of refeeding, significant adaptative changes had occurred in both the relative rates of synthesis and in enzyme concentrations. Thus exocrine pancreatic protein synthesis can be modulated as early as 2 h after refeeding and this modulation is followed by adaptative changes in pancreatic enzyme content.