ALCOHOLS ENHANCE VACUOLAR ATPase TRANSLOCATION AND ZYMOGEN ACTIVATION IN CAERULEIN-STIMULATED PANCREATIC ACINAR CELLS

Abstract

The mechanism of alcoholic pancreatitis is not well understood. Pathologic activation of proteases in the acinar cell helps initiate acute pancreatitis. Alcohols can sensitize the acinar cell to this activation. We have shown that the protease activation requires a proton-transporting vacuolar ATPase (vATPase). Activation of the vATPase requires translocation/assembly of the soluble V1 complex onto the membrane V0 complex. Caerulein and carbachol have been shown to effect vATPase V1 translocation to membranes in acini. We hypothesized that the sensitizing effects of alcohols might be mediated by the vATPase. To examine the effects of alcohols on vATPase assembly and activity, isolated rat pancreatic acini were treated with 10−7M caerulein either alone or in the presence of ethanol or butanol [50 mM] for 15 minutes (to measure translocation by immunoblot) or 60 minutes (to measure zymogen activation by fluorogenic assays). Caerulein (10−7M) increased translocation of V1 2-fold compared to controls. This translocation was increased by about 50% with the addition of ethanol or butanol, demonstrating that alcohols enhance caerulein-induced translocation of V1 to membranes. Ethanol and butanol increased caerulein-induced trypsin activation approximately 2-fold compared to caerulein alone; the vATPase inhibitors bafilomycin A1 and concanamycin (100 nM) reduced this enhanced activation to control levels. From these studies we suggest that alcohols might sensitize the acinar cell to protease activation by enhancing the assembly and activity of the vATPase.