Mutation induction by low dose-rate tritium analyzed by a hyper–sensitive mutation detection system

Abstract

Assessment of biological effects of low dose and/or low dose-rate radiation is an important subject for radiation safety. To clarify the dose rate effects for low dose exposure, we established a hyper-sensitive mutation detection system. The hyper-sensitive mutation detection system is based on hprt deficient hamster cell line carrying a human X-chromosome. Even if a large deletion occurs on the human X chromosome and several essential genes in neighbor of the hprt are lost, those cells are viable and detected as mutants. We confirmed the system is 50-100-fold sensitive compared to conventional system. The cells were cultured in the medium containing HTO to irradiate with low dose rate. Then, mutation frequencies were calculated from the number of 6-thioguanine-resistant colonies. Our results suggest that induced mutation frequency could not be affected at dose rates over 0.09cGy/h.