Ribosomal Change in Liver after Partial Hepatectomy and Acute Stress

The initial rates of incorporation of amino acids by liver microsomes and ribosomes (prepared without detergent and with polyuridylic acid in place of endogenous messenger RNA) from normal, partially hepatectomized, and acutely stressed (Celite-treated) rats are linear. Removal of part of the liver and stress cause increases in the initial rates of incorporation. The reactivities of liver microsomes and ribosomes with puromycin are also enhanced by partial hepatectomy and acute stress. The enhanced rates of reaction with the antibiotic were observed in the presence and absence of guanosine triphosphate and over a wide range of Mg++ concentrations. The changes in reactivity with puromycin parallel the changes in vitro and in vivo in liver protein synthesis as a function of time after partial hepatectomy and acute stress. When normal liver microsomes are treated with 1% deoxycholate, the initial rates of incorporation of 14C-leucine and 3H-puromycin are raised to the levels ordinarily found with untreated preparations from partially hepatectomized and stressed animals. The initial rates with preparations from partially hepatectomized and stressed animals are not affected by the detergent. Similar results are obtained when ribosomes have been treated with deoxycholate. These results suggest that liver ribosomes contain a factor that regulates peptide bond synthesis or the attachment of aminoacyl transfer RNA. Removal of part of the liver and acute stress may reduce the function of the regulatory factor, and deoxycholate may remove it from the ribosome.