Persistence of genetic damage in mice exposed to low dose of X rays

Purpose: The aim of this work was to evaluate the persistence of genetic damage in CBA/J mice treated with a single irradiation of 0.1 or 1 Gy of X rays. Materials and methods: Peripheral blood was collected from irradiated and control mice after 30 min, 24 h, 7 days, 1, 3 and 6 months from exposure and analysed by comet assay. To investigate if the whole-body irradiation affect DNA repair, half of the sampled blood cells were in vitro-irradiated with additional 4 Gy and immediately analysed. Six months from exposure haematopoietic organs were sampled for measuring apoptotic index. Results: In mice exposed to I Gy genetic damage was initially high and decreased during the experimental-time, while in the 0.1 Gy group damage, at first low, persisted and slightly increased. The 0.1 Gy-irradiated mice showed also a time-dependent increasing sensitivity to the in vitro-irradiation. Six months after whole-body irradiation, the percentage of apoptotic cells observed in haematopoietic compartments from 0.1 Gy-irradiated mice was significantly higher compared to controls and to I Gy mice. Conclusions: Results demonstrated that a single exposure to low-dose might induce long-term damage. Persistence of genetic damage might have relevant implications for estimating risk for low doses.