Abstract
An adaptive response induced by low dose-rate long-term irradiation in mice were evaluated in terms of the amount of DNA damage. C57BL/6N female mice were irradiated with 0.5Gy of137Cs-γ rays at 1.2mGy/hr. Then challenge dose (0.5, 1 or 2Gy) was given. For detection of initial DNA damage, we modified single cell gel electrophoresis technique (comet assay). A certain reduction in the amount of DNA damage was observed in pre-irradiated mice spleen cells compared to mice which received the challenge dose only; an adaptive response in terms of DNA damage was induced by low dose-rate long-term irradiation in mice.
One of the possibilities for the mechanism of reduction of initial DNA damage was an enhancement of antioxidative capacity which would protect DNA from injury by reactive oxygen species. Therefore, we measured the level of antioxidants in the spleen of mice irradiated with 0.5Gy at the low dose-rate; a significant increase in the gene expression of catalase was observed. These results suggest that induction of the antioxidants was involved in the adaptive response in terms of DNA damage in mice irradiated with the low dose-rate irradiation.
