title: Repair of ionizing radiation DNA base damage in ataxia-telangiectasia cells.
abstract: Micrococcus luteus endonuclease sensitive sites were measured by alkaline elution in normal human and ataxia-telangiectasia (AT) fibroblasts after ionizing radiation. Due to the sensitivity of this assay, repair of base damage after 3 to 6 kilorads has been measured after oxic or hypoxic radiation. With 5.5 kilorads of oxic radiation, more than 50% of the base damage was removed after 1.5 h of repair incubation in all cells, including exr+ and exr- AT cells, and approximately 75% was removed by 4 h. After 3 or 4.5 kilorads of hypoxic X-irradiation, repair was equivalent in normal and exr- AT cells. This study included three exr- AT strains which have been reported to be deficient in the removal of gamma-ray base damage at higher doses. Since these strains repaired ionizing radiation base damage normally at lower doses, which are more relevant to survival, it is concluded that the X-ray hypersensitivity of AT cells is probably not related to the repair of base damage.
mesh_terms: D001260:Ataxia Telangiectasia / Q000378:metabolism*; D002478:Cells, Cultured; D004247:DNA / Q000528:radiation effects*; D004260:DNA Repair; D004720:Endonucleases / Q000494:pharmacology; D005720:Gamma Rays; D006801:Humans
chemical_list: D004247:DNA; D004720:Endonucleases