Abstract
Tanaka et al. (Radiat. Res., 160, 376-379, 2003) have carried out continuous low-dose-rate irradiation for approximately 400-days on 4000 SPF mice (B6C3F1), and observed no significant shortening of life spans of mice irradiated with gamma rays of the dose-rate 0.05 mGy/d. This result indicates that the biological defense systems could, at least, reduce the damages caused by low-dose-rate radiation in such range to the residuals that are not capable of inducing any significant life span-shortening effect. Although a biological defense system involving p53 is known to play a pivotal role in response to radiation of high doses, the defense system against low-dose-rate irradiation is obscure. We investigated gene expression profiles in the kidney of C57BL/6J mice irradiated under a similar condition to that of Tanaka et al. The mice were irradiated with for 485 days at the dose-rates of 0.043 mGy/d, 0.86 mGy/d, 17 mGy/d. AS a result, 9, 53, 54 genes were identified to be altered in expression level with the fold-change larger than 1.5 for the dose rates 0.043 mGy/d, 0.86 mGy/d, 17 mGy/d, respectively. Among genes altered in expression level, 2 genes were commonly altered for the dose rates 0.043 mGy/d and 0.86 mGy/d, and 14 genes were commonly altered for the dose rates 0.86 mGy/d and 17 mGy/d. No gene was commonly altered for the dose rates 0.043 mGy/d and17 mGy/d. We will analyze the function of genes altered in expression level, and a defensive response to low-dose-rate radiation will be examined.
