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  • Title: Differential increases in syntheses of newly identified trypsinogen 2 isoforms by dietary protein in rat pancreas.
    Author: Hara H, Shiota H.
    Journal: Exp Biol Med (Maywood); 2004 Sep; 229(8):772-80. PubMed ID: 15337831.
    Abstract:
    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.
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