Effect of whole-body irradiation on the synethesis of ribonucleic acid associated with nuclear ribonucleoprotein particles of rat liver.

Synthesis of the RNA of rat liver nuclear RNP particles ("informofers") was studied within 12 hrs after 1930 rad whole-body gamma-irradiation. 14C-orotic acid was administratered intravenously and nuclear RNP particles were extracted by 0.1 M and by 0.3 M salt solutions at pH 8.0. Radioactivity of the RNP particles 1.5--2.0 times higher than that of the unirradiated controls up to 6 hrs after irradiation, exhibiting a maximum at the first hour. The labelling of the 0.3 M RNP particles was higher and chased less rapidly than that of the 0.1 M RNP particles. The RNA to protein ratio and the protein composition of the RNP the RNP particles did not change after irradiation as examined by CsCl density gradient centrifugation and by acrylamide gel electrophoresis, respectively. In the cytoplasm enhanced synthesis of rapidly labelled RNA sedimenting with 40 S cytoplasmic RNP paricles could also be demonstrated after irradiation. It is concluded that the synthesis of messenger-type RNA associated with liver nuclear RNP particles increases and more RNA is transferred from the nucleus to the cytoplasm after whole-body irradiation.