The role of nuclei, polyribosomes and cytosol factors in the onset of the acute-phase reaction in the liver cell.

Nuclei isolated from livers of turpentine-treated rats show an increased RNA synthesis, reaching a maximum at 10 h after treatment. The stimulation affects both alpha-amanitin-resistant and alpha-amanitin-sensitive activities, suggesting that pre-ribosomal and pre-messenger RNA formation are activated at the same time and to the same extent. The amount of ribosomal RNA, which is still normal 10 h after treatment, increases significantly at 24 h, but the increase is limited to the bound ribosomes, in keeping with the fact that the acute phase reactants are export proteins. These ribosomes, however, are not more active per se and the stimulation of protein synthesis in cell-free preparations depends essentially on an increased activity of soluble factors located in the cytosol. In living cells these soluble factors co-operate with an increased amount of some specific mRNAs and an expanded population of membrane-bound polyribosomes, thus leading to the increased protein synthesis peculiar to the liver of turpentine-treated rats.