Acute effects of ethanol intake on albumin and total protein synthesis in free and membrane-bound polyribosomes of rat liver.

Controversial results have been reported in the last few years concerning the effects of ethanol on hepatic protein synthesis. In most of the studies no distinction has been made between the synthetic capabilities of the polyribosomes and the secretory product of labelled protein by the hepatocytes. In order to assess the influence of a single feeding of ethanol on the synthesis of albumin and total protein by the polyribosomes of rat liver, free and membrane-bound polyribosomes were isolated quantitatively from rats given 4--8 g ethanol per kg body weight 3--5 h before killing. The following results were obtained: (1) No difference was found in yield and size of free and membrane-bound polyribosomes isolated from control and ethanol-treated rats. The abilities to synthesize albumin and total protein were also equal for polyribosomes from both groups. (2) Addition of 1% ethanol to the incubation mixture of protein synthesis lowered albumin and total protein synthesis by 20%. No effect was observed with 0.5% ethanol. (3) Cell sap prepared from ethanol-treated rats contains a factor or factors which stimulate protein synthesis (10--15%). (4) The albumin mRNA sequence content was not changed in free and membrane-bound polyribosomal RNA fractions of ethanol-treated rats as compared to the control animals.