Alterations in the Radiosensitivity of CHO Cells by Anisotonic Treatments: Correlations between Cell Lethality and Chromosomal Aberrations

Abstract

The frequency of chromosomal aberrations and cell lethality induced in synchronous CHO cells by X irradiation alone or X irradiation combined with a treatment of 0.05) or 1.5 M NaCl has been examined. Treatment with hypotonic 0.05 M NaCl increased the radiosensitivity, i.e., decreased the D/sub 0/ in M (D/sub 0/ from 87 to 61 rad), in G/sub 1/ (D/sub 0/ from 156 to 122 rad) and in S (D/sub 0/ from 165 to 128 rad). Exposure to hypertonic (1.5 M) NaCl decreased the radiosensitivity in G/sub 1/ and S; i.e., increased the D/sub 0/ in G/sub 1/ (D/sub 0/ from 156 to 182 rad) and in S (D/sub 0/ from 165 to 232 rad), while exposure to 1.5 M NaCl increased the radiosensitivity in mitosis (D/sub 0/ from 87 to 78 rad). The 0.05 or 1.5 M salt treatments had no observable effect on the radiation-induced division delay. The appearance of tetraploid cells following treatment of mitotic cells with 1.5 M NaCl indicates that the hypertonic treatment probably had a deleterious effect on the mitotic apparatus. Except for a decrease in the frequency of radiation-induced chromosomal aberrations in mitotic cells treated with 1.5 M NaCl, the changes in themore » frequency of chromosomal aberrations caused by the salt treatments correlated well with the changes in lethality delineated above. These positive correlations can be illustrated best by a plot of the logarithm of survival versus aberration frequency where the data points fell on a straight line havinga D tilde/sub 0/ of 0.8 aberration per cell. The salt-induced changes in cellular radiosensitivity are hypothesized to be caused by changes in the indirect effect of radiation, associated with free radicals produced in water and interacting in chromatin.« less