Differential effect of chronic ethanol administration on rates of protein synthesis on free and membrane-bound polysomes in vivo in rat liver during dependence development.

Administration of ethanol thrice daily to rats in amounts sufficient to induce a high degree of physical dependence resulted in a 20% decrease in the rate of protein synthesis on liver membrane-bound polysomes in vivo after 3 days of treatment without affecting the rate on free polysomes. The inhibition was attributable to a decrease in the rate of polypeptide elongation as evidence by comparable decreases in nascent chain synthesis and completed protein release without any change in leucine uptake by liver. Chronic ethanol treatment did not affect the quantity or distribution of free and membrane-bound polysomes, the DNA concentration, or the weight of liver. The inhibition of protein synthesis on membrane-bound polysomes cannot, therefore, be readily ascribed to ethanol-induced nutritional deficiencies or to some nonspecific toxic effect of ethanol.