Acute effect of ethanol on membranes of the endoplasmic reticulum and on protein synthesis in rat liver.
The acute effect of ethanol on the membranes of hepatic endoplasmic reticulum, on the in vitro protein-synthetic activities of hepatic free and membrane-bound polyribosomes and on the plasma proteins of rats fasted overnight was investigated. Ethanol (0.75 g/100 g body weight) was tube-fed as a 50% (v/v) solution in saline 3 hr before sacrifice. Hepatic endoplasmic reticulum membranes from control and ethanol-treated rats were compared using the following techniques: (1) lactoperoxidase-catalyzed radioiodination of proteins and sodium dodecylsulfate-polyacrylamide gel electrophoresis, and (2) measurement of 14C-choline incorporation into membranes. Hepatic microsomal membranes from ethanol-treated rats incorporated in vitro les 125I into total proteins (as well as into the 55,000 molecular weight proteins) and incorporated in vivo less 14C-choline into microsomal membranes than membranes of control rats. Ethanol administration inhibited in vivo incorporation of 14C-leucine or 14C-phenylalanine into liver protein and plasma albumin and globulin. The data also indicate that an acute dose of ethanol reduced the in vitro protein-synthetic activity of hepatic membrane-bound polyribosomes, while free polyribosomes were relatively unaffected.