Abstract
In order to clarify the characteristics of DNA damage and dose-rate effect induced by neutron irradiation, the induction of DNA double strand breaks (DNA-DSBs) was investigated in CHO-K1 cells and xrs5 cells (Ku-80 deficient mutant cells). The cells were incubated according to the ordinary procedures, and then exposed to a mixed field of neutron and gamma-ray (total doses: approximately 2Gy/50min and 2Gy/10min) in the D2O neutron irradiation facility of Kyoto University Reactor. The cells were also irradiated with 60Co gamma-ray (approximately 2Gy/50min) as a control. At one hour after irradiation, the cells were fixed with 4% formalin and stained immunochemically with gamma-H2AX or 53BP1 antibody. The number of DNA-DSBs was determined by counting the gamma-H2AX or 53BP1 foci. The numbers of gamma-H2AX or 53BP1 foci induced by gamma-ray irradiation increased with the dose up to 2Gy. The number of 53BP1 foci was larger in the xrs5 cells than in the CHO-K1 cells, in both of neutron and gamma-ray irradiations. This may suggest that the repair of DNA-DSBs induced by neutron was impaired in xrs5 cells, as well known in gamma-ray irradiation.
