A possible mechanism for gallstone pancreatitis: repeated short-term pancreaticobiliary duct obstruction with exocrine stimulation in rats

Abstract

The effects of single and repeated short-term (4 hr) obstruction of pancreaticobiliary duct (PBDO), with or without exocrine stimulation (intraductal hypertension) by cerulein infusion (0.2 micrograms/kg.hr), on the exocrine pancreas were evaluated in the rat. Single blockage of pancreaticobiliary duct for 4 hr caused a significant rise in serum amylase levels, pancreatic water content, and redistribution of lysosomal enzyme, cathepsin B from the lysosomal fraction to the zymogen fraction, which was considered to mean the colocalization of lysosomal enzymes with pancreatic digestive enzymes in the same subcellular compartment in acinar cells. In addition, the accelerated lysosomal and mitochondrial fragility was observed in the single pancreaticobiliary-duct-obstructed animals. Moreover, the repeated PBDO for 4 hr (2 hr in each obstruction and 1 hr of free flowing of pancreaticobiliary juice between two obstructions) caused more marked changes in almost the all parameters, and the repeated PBDO with intraductal hypertension caused an activation of trypsinogen in the pancreas, making more marked changes in almost the all parameters than the repeated PBDO only group. These results indicate that the present model of repeated PBDO with exocrine stimulation seems to be a pertinent model for gallstone pancreatitis in humans, and that redistribution of lysosomal enzymes and subcellular organellar fragility seem to play an important role in the pathogenesis of pancreatic injuries induced by PBDO, particularly by repeated PBDO with exocrine stimulation, probably via activation of trypsinogen to trypsin by lysosomal enzyme, cathepsin B.