Cultured mouse SR-1 cells exposed to low dose of γ-rays become less susceptible to the induction of mutagenesis by radiation as well as bleomycin

The effect of pre-exposure of cultured mouse SR-1 cells to a low dose of γ-rays on the induction of mutations at the hprt locus by subsequent high dose radiation or bleomycin was studied. When cells were pre-exposed to 0.01 Gy γ-rays, the induction of mutations by a 3 Gy γ-ray dose given 18 or 24 h later was significantly reduced as compared with those which did not receive the low dose pre-exposure. When cells were challenged with 5 or 10 μg/ml bleomycin for 12 h, which can produce double strand breaks in DNA, instead of 3 Gy γ-rays, a similar mutagenetic adaptive response was observed. The authors conclude that this resistance to radiation- or bleomycin-induced mutation is attributed to the induction of a DNA double-strand break repair mechanism. (Author)