Abstract
Previously, p53-dependent decrease of white blood cells in peripheral blood in mice by gamma ray irradiation at middle-dose-rate (MDR) [400 mGy/22h/day(18.2 mGy/h)] was reported. However, the effects of secreted molecules in serum from mice irradiated by low-dose-rate (LDR) or MDR gamma ray were not well investigated. In the present experiment, serum from mice irradiated by LDR or MDR gamma ray, were characterized. A cell-based-assay, which is a new method for measuring activity of substances in serum thorough gene expressions levels in mouse embryonic fibroblasts (MEFs), was performed. Expressing genes having two-fold higher gene-expressions levels in MDR irradiated mice than non-irradiated mice were analyzed for gene-expressions patterns. Moreover, the serum from LDR [(20 mGy/22h/day (0.91 mGy/h)] irradiated mice for 400 days were also used for the analysis. Numbers of identified genes in mice irradiated by MDR irradiation for 10 and 20 days with the total doses of 4 and 8 Gy, were 613 and 1,202, respectively. Caveolin signal pathway and insulin-receptor-signal pathway was found by pathway analysis in these genes. Interestingly, these genes-expressions patterns were quite similar to those of disease such as lipid metabolism or coronary artery disease. Moreover, the protein expression of Lipocalin2 in MEFs after adding of serum, which was reported to be a gene influenced by high-dose-rate gamma ray irradiation, was irreversibly decreased by MDR gamma ray irradiation for 8 Gy, while the change of Lipocalin2 in serum induced by LDR irradiation for 400 days for 8 Gy was not observed. Present results indicated the activity of secreted molecules in mouse serum was quantitatively and qualitatively changed by gamma ray irradiation at MDR, which might be influenced to metabolism. This study was performed under contract with the Aomori Prefectural Government, Japan.
