<SESSION>A NOVEL CHROMOSOMAL RESPONSE TO LOW-LEVEL TRITIUM : ADAPTIVE RESPONSE INDUCED BY IONIZING RADIATION IN CULTURED CHINESE HAMSTER CELLS

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Pre-treatment with low doses of β-rays from incorporated tritiated thymidine (^3H-dThd) or of Co-60 γ-rays (1 or 5 cGy) rendered actively growing Chinese hamster V79 cells more resistant to the induction of micronuclei or sister chromatid exchanges (SCEs) by a subsequent high dose of γ-rays (1 Gy). This adaptive response to ionizing radiation can be induced by an optimal range of low doses of ^3H β-rays, but not by much lower or higher adapting doses. The induced resistance was abolished after the ^3H-adapted cells had divided once or when 3-aminobenzamide (3AB) was given before the challenging doses, which suggests a short life for the adaptive response and the involvement of poly (ADP-ribose) polymerase in this response. The ^3H-adapted cells were somewhat resistant to SCE-induction but not to micronucleus-induction by challenge doses of high LET radiation from the reactor, KUR. Full expression of the adaptive response induced by the exposure to low doses of ^<60> Co γ-rays occurred 4 hafter the adapting dose. The cells pre-exposed to low doses of γ-rays showed cross-resistance to challenge doses of γ-rays, itself and also of mitomycin C (MMC) and near ultraviolet light (UV-B, 313 nm), but not to those of ethyl methanesulfonate (MES) or cis-platinum (II) diammine dichloride (cisplatin) for SCE induction. These results suggest that the adaptive response to ionizing radiation is different from that to alkylating agents, and that it may be mediated through a hitherto unknown inducible DNA-repair network.
核融合科学研究所の論文

<SESSION>A NOVEL CHROMOSOMAL RESPONSE TO LOW-LEVEL TRITIUM : ADAPTIVE RESPONSE INDUCED BY IONIZING RADIATION IN CULTURED CHINESE HAMSTER CELLS

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