Two distinct adaptive responses in the synthesis of exocrine pancreatic enzymes to inverse changes in protein and carbohydrate in the diet

Abstract

Rates of synthesis of 16 individual pancreatic exocrine proteins; tissue concentrations of amylase, trypsinogen, and chymotrypsinogen; and morphological assessment of pancreatic acinar cells were studied in the exocrine pancreas in response to inverse changes in protein and carbohydrate in the diet, administered for 12 days. Two distinct patterns of response were observed. During adaptation to diets containing normal protein (22%) or increased levels of protein (30, 45, 64, and 82% protein) and correspondingly decreased levels of carbohydrate, amylase and the majority of protease zymogens were synthesized in direct proportion to the nutritional substrates carbohydrate and protein, respectively, in the diet. With increases in dietary protein, anticoordinate patterns of response in the synthesis of exocrine isoenzymes were observed: 0.4- to 2.0-fold increases in trypsinogen forms 1 and 2, chymotrypsinogen forms 1 and 2, proelastase 1, and procarboxypeptidases A and B; 5- to 7-fold decreases in amylase forms 1 and 2; and insignificant changes in trypsinogen 3, proelastase 2, lipase, and ribonuclease. During adaptation to diets containing normal protein (22%) or decreased levels of protein (0 or 10% protein) and correspondingly increased levels of carbohydrate, amylase and the majority of protease zymogens were synthesized in inverse proportion to nutritional substrates in the diet.(ABSTRACT TRUNCATED AT 250 WORDS)