EN
The L5178Y (LY) murine lym phoma sublines LY-R and LY-S are dif fer en tially sen si tive to ion iz ing ra di a tion. The high ra di a tion sen si tiv ity of LY-S cells is re lated to impaired rejoining of DNA double strand breaks. We found previously that the g-ray-induced base dam age is higher in the more radiosensitive LY-S subline. Here, we ex am ine the role of the re pair of ion iz ing ra di a tion in duced base dam age in re la tion to the radiosensitivity dif fer ence of these sublines. We used the GS/MS tech nique to es ti mate the re pair rates of six types of base damage in g-irradiated LY cells. All mod i fied DNA bases iden ti fied in the course ofthis study were typ i cal for ir ra di ated chromatin. The to tal amount of ini tial base dam age was higher in the ra di a tion sen si tive LY-S subline than in the ra di a tion re sis tant LY-R subline. The re pair rates of 5-OHMeUra, 5-OHCyt, 8-OHAde were sim i lar in both cell lines, the re pair rates of FapyAde and 8-OHGua were higher in the radiosensitive LY-S cell line, whereas the re pair of 5-OHUra was faster in its radio resistant coun ter part, the LY-R. Al to gether, the re pair rates of the g-ray-induced DNA base dam age in LY sublines are re lated nei ther to the ini tial amounts of the dam aged bases nor to the dif fer en tial le thal or mutagenic ef fects of ion iz ing ra di a tion in these sublines.