Changes in Both the Membrane and the Enzyme Content of Individual Zymogen Granules are Associated with Sodium Taurocholate-Induced Pancreatitis in Rats

Abstract

1. After monitoring the changes associated with necrotizing acute pancreatitis in rats from early stages to 24 h after infusion of 5% sodium taurocholate in the choledocus, we characterized by flow cytometry the zymogen granules that still remained in the pancreas 18 h after sodium taurocholate infusion in order to explore whether alterations in the enzyme content and/or in the composition of the granule membrane could be related to the intracellular mechanisms involved in the development of necrotizing acute pancreatitis. 2. Significant increases in the haematocrit, plasma and peritoneal exudate amylase levels and oedema were observed from the third hour after 5% sodium taurocholate infusion onwards. Additionally, cell alterations such as hypergranulation, dilatation of the endoplasmic reticulum and autophagic vacuoles were found 3 and 6 h after infusion. DNA decrease, degranulation and necrosis were observed from 12 h after sodium taurocholate infusion onwards. 3. Flow cytometric measurements of zymogen granules isolated from rat pancreas 18 h after 5% sodium taurocholate infusion revealed a significant decrease in their internal complexity without major changes in their size. Double staining of granules with Tetragonolobus purpureus lectin, which specifically binds l-fucose and specific anti-trypsinogen or anti-amylase antisera, showed that rats with induced pancreatitis have decreased amounts of l-fucose in the membrane glycoconjugates and lower enzyme content (70% and 30% less for trypsinogen and amylase respectively). 4. A decrease in l-fucose in the membrane together with membrane abnormalities observed by electron microscopy in zymogen granules isolated 18 h after sodium taurocholate infusion indicate an altered synthesis of new granules or lysis of preformed zymogen granules which would favour differential loss of granular enzymes, mainly tripsinogen, which in turn could increase the severity of disease.