DNA-synthesis in Nuclei Isolated from Regenerating Rat Liver after Whole-body Irradiation

Summary

Incorporation of tritiated thymidine into DNA of nuclei isolated from the regenerating livers of rats given 800 r of whole-body radiation 24 hours after partial hepatectomy has been studied in the presence of a DNA-synthesizing enzyme system. Immediately after irradiation no difference in incorporation was demonstrable between irradiated and non-irradiated liver nuclei. With increasing time after irradiation, up to 24 hours, incorporation became progressively depressed. At 24 hours after irradiation, incorporation was depressed to the same extent after doses of 200 to 3000 r. Incorporation into nuclei of liver from non-hepatectomized rats was unaffected 24 hours after a dose of 800 r.

In contrast to the findings with isolated nuclei, DNA extracted from irradiated regenerating liver, 24 hours after a dose of 800 r, incorporated tritiated thymidine to the same extent as did DNA extracted from non-irradiated regenerating liver.

Mechanisms by means of which these findings may be explained are discussed.