Alteration of γ-ray-induced Chromosome Aberration by 0·5 m NaCl in Chinese Hamster Cells

Abstract

Hypertonic treatment (0·5 m NaCl in phosphate-buffered saline, pH 7·2) at 37°C for 20 min slightly delayed the mitotic frequency for non-irradiated cells in G₁ and G₂ phases. The mitotic frequency for irradiated cells in G₂ was delayed by hypertonic treatment, and that in G₁ was slightly delayed by hypertonic treatment. Hypertonic treatment in non-irradiated cells did not induce any chromosomal or chromatid aberrations in either G₁ or G₂. Chromosomal aberrations caused by γ-irradiation were slightly enhanced by hypertonic treatment, and chromatid aberrations were markedly enhanced by hypertonic treatment. The enhancement ratio of γ-irradiation-induced chromatid breaks and exchanges was 1·4 and 3·0, respectively. This cell cycle dependency of chromosome aberrations induced by postirradiation hypertonic treatment was the same as that of cell survival. These findings suggested that hypertonic treatment modifies the rejoining of DNA strand breaks in G₂, but slightly modifies that in G₁.