Stability of messenger ribonucleic acid of free and membrane-bound polyribosomes of the livers of rats treated with ethionine.

Administration of ethionine to female rats results in disaggregation of free and membrane-bound polyribosomes and inhibition of protein synthesis in the liver. The administration of adenine and methionine to ethionine-treated rats reverses these effects, even after actinomycin D treatment which inhibits new RNA synthesis. The membrane-bound polyribosomes show greater recovery of the state of aggregation and of in vitro protein synthesis than do the free polyribosomes of rat liver. The messenger RNA (mRNA) in the recovering membrane-bound polyribosomes appears to come from endoplasmic reticulum membranes and is not related to increased nucleocytoplasmic translocation of existing mRNA. Initiation factors-dependent stimulation of polyphenylalanine synthesis by ribosomes and by initiation factors of membrane-bound polyribosomes is increased more than the synthesis by ribosomes and by initiation factors of free polyribosomes in the livers of ethionine-treated rats receiving actinomycin D and adenine plus methionine. Our results suggest that stable mRNA associated with membranes remains in the rat liver after injury by ethionine, and during recovery induced by adenine and methionine, the mRNA is utilized to reform membrane-bound polyribosomes.