CERULEIN-INDUCED IN-VITRO ACTIVATION OF TRYPSINOGEN IN RAT PANCREATICACINI IS MEDIATED BY CATHEPSIN-B

Background & Aims: One of the central, unresolved issues in the pathog enesis of acute pancreatitis is the uncertainty regarding the mechanis ms responsible for the premature intrapancreatic activation of digesti ve enzyme zymogens. The aim of the current study was to develop and ch aracterize an in vitro system that might mimic the events leading to t rypsinogen activation within the pancreas during pancreatitis. Methods : Activation of trypsinogen in response to stimulation with cerulein w as quantitated in isolated rat pancreatic acini. Results: Activation o f trypsinogen was detected within 10 minutes of exposing isolated rat pancreatic acini, in Ca2+-containing buffer, to a supramaximally stimu lating concentration of cerulein in vitro. Complete inhibition of panc reatic cathepsin B activity with E-64d, a specific, potent and irrever sible cathepsin B inhibitor, prevents cerulein-induced in vitro trypsi nogen activation. Conclusions: In vitro activation of trypsinogen can be detected when pancreatic acini are exposed to a supramaximally stim ulating dose of cerulein. The results using this in vitro system suppo rt the hypothesis that the appearance of active trypsin within the pan creas during the early stages of cerulein-induced pancreatitis reflect s activation of trypsinogen by the lysosomal hydrolase cathepsin B.