EFFECT OF CHRONIC ETHANOL-CONSUMPTION ON GLYCOSYLATION PROCESSES IN RAT-LIVER MICROSOMES AND GOLGI-APPARATUS

Previous studies have demonstrated that acute ethanol intoxication aff ects various steps of protein glycosylation at the level of rat liver endoplasmic reticulum and Golgi apparatus. The aim of this investigati on was to demonstrate whether chronic ethanol intake can induce defini tive changes of liver glycoprotein processing. Rats were given ethanol by liquid diet for 8 weeks. At the end of this period the triglycerid e levels in liver homogenate and microsomes were significantly higher than in controls. Isolated hepatocytes prelabelled with [H-3]Na palmit ate and [C-14]glucosamine showed a significant storage of the lipid an d carbohydrate radioactivity in microsomes and Golgi apparatus and a s ignificant impairment of labelled glycolipoprotein secretion. Changes of the glycosylation steps were observed both in endoplasmic reticulum and in Golgi apparatus: in the former the levels of dolichyl phosphat e, which is rate-limiting for the synthesis of glycoprotein, showed a significant reduction; in the latter the activity of the main enzymes responsible for the terminal glycosylation process was significantly d ecreased. These data suggest that an impairment of glycoprotein matura tion may be involved in the pathogenesis of liver injury induced by ch ronic ethanol intake.