Differential increases in syntheses of newly identified trypsinogen 2 isoforms by dietary protein in rat pancreas.
We have found that dietary protein markedly induced pancreatic serine protease activity via a mechanism independent of luminal trypsin activity in pancreaticobiliary-diverted (PBD) rats. The aim of this study was to examine the effects of dietary protein on the synthesis of trypsinogen isoforms by comparing in vivo incorporation of [35S] L-methionine into isoform proteins in PBD and sham-operated rats. A small duodenal segment including the ampulla of Vater was sectioned and transposed to the upper ileum with end-to-side anastomosis (PBD) or duodenal transection was followed by reanastomosis (sham) in male Sprague-Dawley rats. After recovery, PBD and sham rats were fed a 25% or 60% casein-sucrose-based diet (NC or HC) for 14 days. Rats were then intravenously injected with [35S] L-methionine (15 MBq/kg body weight) 30 mins before being sacrificed for analysis of pancreatic enzymes by two-dimensional SDS-polyacrylamide gel electrophoresis. By using electrophoresis with narrow range of isoelectric focusing (pI 4.5-5.5), five trypsinogen 2 (2-x) isoform spots were identified using both [35S] incorporation and Coomassie brilliant blue (CBB) staining in PBD rats, but not in sham rats. N-terminal sequences of these trypsinogen 2-x spots were identical to known rat trypsinogen 2 with the exception that the third valine was changed to isoleucine in one isoform. In PBD rats, feeding of HC specifically increased the [35S] and CBB intensities of these trypsinogen 2-x isoforms and trypsinogen 3. The degree of induction of the five trypsinogen 2-x molecules by HC varied greatly. Trypsinogen 1 and 4, which are the major trypsinogens in normal rats, showed no changes. We conclude that increases in synthesis of a few newly identified trypsinogen 2-x isoforms mainly contribute to the induction of trypsin activity in the pancreas by HC in PBD rats.
Hara
Hiroshi
H
Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan. hara@chem.agr.hokudai.ac.jp
Shiota
Hiromichi
H
D000714:Anastomosis, Surgical; D000818:Animals; D001646:Bile / Q000201:enzymology; D002364:Caseins; D004044:Dietary Proteins / Q000494:pharmacology*; D004386:Duodenum / Q000601:surgery; D015180:Electrophoresis, Gel, Two-Dimensional; D007082:Ileum / Q000601:surgery; D007527:Isoenzymes / Q000096:biosynthesis / Q000302:isolation & purification; D008297:Male; D010179:Pancreas / Q000201:enzymology*; D010189:Pancreatic Juice / Q000201:enzymology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014357:Trypsin; D014362:Trypsinogen / Q000096:biosynthesis* / Q000302:isolation & purification
D002364:Caseins; D004044:Dietary Proteins; D007527:Isoenzymes; C064831:PRSS2 protein, human; D014362:Trypsinogen; D014357:Trypsin