Oxidative stress on the male reproductive organs of wild mice collected from an area contaminated by radioactive materials in Fukushima

The Fukushima Daiichi Nuclear Power Plant accident caused the release of large amounts of radioactive material into the environment. Radiation from radionuclides cause DNA lesions, mainly via oxidation, which adversely affect wild organisms by damaging their germ cells. Here, we investigated the effects of radiation on the reproductive organs of Japanese field mice (Apodemus speciosus) by estimating the dose rate of radiation exposure, the accumulation of DNA lesions, and the expression of DNA repair enzymes. In highly contaminated areas, mouse testes received a radiation dose rate > 0.1 mGy/d. According to the International Commission on Radiological Protection, there is a very low probability of effects in the reference rat species at this exposure level. The results of the current study do not definitively conclude that the expression of 8-oxoguanine DNA glycosylase 1 and superoxide dismutase in mouse testes increase with dose rate and lifetime dose. However, 8-hydroxy-2′-deoxyguanosine accumulation increases in a dose rate- and lifetime dose-dependent manner in mouse testes, but is not observed in the sperm of the cauda epididymis. These results suggest that, although DNA lesions occurred in male germ cells of Fukushima mice, most were successfully repaired by DNA repair enzymes at the observed gene expression level.