Even today, 70 years after Hiroshima and accidents like Chernobyl and Fukushima, we still have limited knowledge about health effects of low dose rate (LDR) radiation. Despite their human relevance after occupational and accidental exposure, only few animal studies on the genotoxic effects of chronic LDR radiation have been performed. Selenium (Se) is involved in oxidative stress defense, protecting DNA and other biomolecules from reactive oxygen species (ROS). It is hypothesized that Se deficiency, as it occurs in several parts of the world, may aggravate harmful effects of ROS-inducing stressors such as ionizing radiation. We performed a study in the newly established LDR-facility Figaro on the combined effects of Se deprivation and LDR gamma exposure in DNA repair knockout mice (Ogg1-/-) and control animals (Ogg1+/-). Genotoxic effects were seen after continuous radiation (1.4 mGy/h) for 45 days. Chromosomal damage (micronucleus), phenotypic mutations (Pig-a gene mutation of RBCCD24-) and DNA lesions (single strand breaks/alkali labile sites) were significantly increased in blood cells of irradiated animals, covering three types of genotoxic activity. This study demonstrates that chronic LDR gamma radiation is genotoxic in an exposure scenario realistic for humans, supporting the hypothesis that even LDR gamma radiation may induce cancer.
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