Chronic ethanol administration selectively impairs endocytosis in the rat exocrine pancreas

Release of GP2, a glycosyl phosphatidylinositol-linked protein on the apical plasma membrane of the pancreatic acinar cell, is associated with activation of endocytosis. Released GP2 is also an integral component of intraductal plugs in patients with alcohol-induced chronic pancreatitis. Our purpose was to determine the effect of ethanol on exocytosis and endocytosis and its association with release of membrane-bound GP2. Rats were fed Lieber-DeCarli diets with and without ethanol for 2 weeks. Endocytosis was then assessed in acini by measuring horseradish peroxidase (HRP) uptake, GP2 release by Western blotting, and exocytosis by measuring amylase release. In ethanol-fed rats, HRP uptake was inhibited by 90% compared to that in control rats. In contrast, no significant difference in cholecystokinin-stimulated amylase secretion was found. In vitro, ethanol inhibited HRP uptake in a dose-dependent manner, with 50% inhibition at 50 mM ethanol. Despite the inhibition of endocytosis, GP2 release increased linearly over 60 min and was significantly higher from acini incubated with ethanol compared to controls. These data indicate that ethanol selectively inhibits endocytosis in pancreatic acinar cells. The release of GP2 into the pancreatic duct was no longer coupled to endocytosis in animals fed ethanol.