ALTERATION OF GAMMA-RAY-INDUCED CHROMOSOME ABERRATION BY 0-CENTER-DOT-5 M NACL IN CHINESE-HAMSTER CELLS

Hypertonic treatment (0.5 M NaCl in phosphate-buffered saline, pH 7.2) at 37 degrees C for 20 min slightly delayed the mitotic frequency for non-irradiated cells in G(1) and G(2) phases. The mitotic frequency f or irradiated cells in G(1) was delayed by hypertonic treatment, and t hat in G(1) was slightly delayed by hypertonic treatment. Hypertonic t reatment in non-irradiated cells did not induce any chromosomal or chr omatid aberrations in either G(1) or G(2) Chromosomal aberrations caus ed by gamma-irradiation were slightly enhanced by hypertonic treatment , and chromatid aberrations were markedly enhanced by hypertonic treat ment. The enhancement ratio of gamma-irradiation-induced chromatid bre aks and exchanges was 1.4 and 3.0, respectively. This cell cycle depen dency of chromosome aberrations induced by postirradiation hypertonic treatment was the same as that of cell survival. These findings sugges ted that hypertonic treatment modifies the rejoining of DNA strand bre aks in G(2), but slightly modifies that in G(1).