[Change in the radiosensitivity of chromosomes during the S-period in cells of regenerating rat liver].

Change in radiosensitivity of chromosomes in the course of the S-period and the degree of the post-irradiation inhibition of DNA synthesis in cells of regenerating rat liver is studied. The frequency of radiation-induced chromosome aberrations at 150-600 r doses was established to vary during the S-period, being the highest at the early stage of this period and the lowest at its late stage. The dependence of the frequency of initiation of chromosome aberrations on the radiation dose is the most conspicuous for cells irradiated in the beginning of the S-period, whereas in the end of the S-period no such dependency is observed. Besides, it is found that the irradiation of animals at 150-600 r doses results in the inhibition of DNA synthesis mainly in the end of the S-period. As it is shown by the comparison of the yield of chromosome aberrations to the inhibition of DNA synthesis, the yield of chromosome aberrations decreases in case of DNA synthesis suppression during the S-period.