Effect of irradiation on the phosphorylation of the nuclear proteins of the liver and thymus of rats

The exposure of the nuclei and chromatin of the rat liver and thymus in vitro to small doses (1 to 5 krad) stimulates, and to high doses (10 to 20 krad) inhibits the protein phosphorylation. Dephosphorylation is only inhibited when thymus nuclei are irradiated. Phosphorylation of the nuclear proteins of the liver and thymus is increased by 37% and 15%, respectively, 15 minutes after the exposure in vivo to a dose of 1 krad. Phosphorylation of histones is most- and of the nuclear sap proteins, least enhanced. A 10-per cent increase in the phosphorylation of the liver nuclei, and a 23-per cent decrease in that of the thymus nuclei, as compared to the controls, are observed two hours after the exposure. A possible relationship between radiation impairment of the nuclear protein phosphorylation and of the RNA synthesis is discussed