Radiation-induced apoptosis in peritoneal resident macrophages of C3H mice

Gamma ray-radiation induced significant apoptosis in peritoneal resident macrophages (PRMs) of C3H/HeJ (C3H) mice, but not in other strains of mice. To investigate the role of DNA damage in the apoptosis, DNA damage was quantified in PRMs by use of the alkaline single-cell gel electrophoresis (Comet) assay. No significant difference was found between C3H and C57Black/6 mice in either radiation-induced DNA damage or repair. Radiation induced apoptosis at the same levels in PRMs of p53 knockout mice and atm knockout mice as those of wild-type C3H mice; however radiation-induced apoptosis was significantly less extensive in the thymocytes of these mutant mice than in those of wild-type mice. Apoptosis was also induced at the same level by an irradiation in PRMs of C3H scid mice as in those of wild-type C3H mice. Therefore it was suggested that radiation-induced DNA damage and TP53, ATM, or DNA-PK-mediated cellular responses occurring downstream thereof were not involved in the radiation-induced apoptotic cell death in C3H mouse PRMs.