LIGATION-INDUCED ACUTE-PANCREATITIS IN OPOSSUMS - ACINAR CELL NECROSIS IN THE ABSENCE OF COLOCALIZATION

Acute necrotizing pancreatitis in opossums after bile and pancreatic d uct ligation (BPDL) is a useful experimental corollary of gallstone-in duced acute pancreatitis in humans. In experimental and human acute pa ncreatitis, a loss of segregation of the lysosomal enzyme cathepsin B and the zymogen proenzyme trypsinogen (colocalization) is implicated a s the triggering event of disease pathogenesis, as cathepsin B can act ivate trypsinogen. The object of this study was to quantitate acinar c ell necrosis and to study subcellular distribution of cathepsin B in B PDL-induced acute necrotizing pancreatitis in opossums. Bile and pancr eatic ducts were ligated separately (no bile reflux) in four opossums, while ducts were dissected in four sham controls. Opossums were kille d 24 hr after operation. three equidistant cross-sectional portions of each opossum pancreas were submitted to histologic examination. In bl inded fashion, each focus of acinar cell necrosis was photographed and quantitated with digitizing morphometry. Numerical density (foci/cm(2 )) and areal density (x10(3) mu m(2)/cm(2)) of focal acinar cell necro sis were determined. differentially centrifuged pancreatic homogenates were assayed for cathepsin B, the lysosomal marker enzyme N-acetylglu cosaminidase, and amylase. Morphometric quantitation of acinar cell ne crosis confirmed development of acute necrotizing pancreatitis after 2 4 hr ob BPDL in opossums. However, colocalization was not observed aft er BPDL, as evidenced by an absence of subcellular shift of cathepsin B activity (and N-acetyl-glucosaminidase activity) from the lysosome-e nriched to the zymogen-enriched subcellular fraction. Amylase activity was increased in subcellular fractions after BPDL. In this experiment al corollary of early gallstone-induced acute pancreatitis, colocaliza tion is not the triggering event of acute necrotizing pancreatitis pat hogenesis, as acinar cell necrosis occurs even in the absence of coloc alization. (C) 1995 Academic Press, Inc.