Abstract
Considering the biological effect of low-dose radiation of heavy charged-particle, the bystander effect will play an important role on the response of irradiated cells. However, analyzing bystander effect requires a method to distinguish irradiated cells and bystander cells. Using microbeam irradiation is a good way to solve this issue. Thus we irradiated CHO-K1 cells with heavy ion microbeam at JAERI-Takasaki, and analyzed its response on the point of view of phosphorylation of histone H2AX.
We used a sample holder whose bottom was made by a thin film of a plastic ion-track-detector, CR-39 (100 μm thick). The CHO-K1 cells were kept in exponential growth phase, and 2500-3000 cells were inoculated within the area of 5 mm x 5 mm at the center of a sample holder. Among the inoculated cells, 25 cells were selected and their positions were stored in the object database. Thereafter the cells were irradiated by 5 count of 40Ar13+ ion microbeam (11.5 MeV/u, LET=1610 keV/μm). The irradiated cells were post-incubated for 30 minutes to 6 hours, then fixed and stained immunohistochemically with antibody specific with γH2AX. The frequency of γH2AX positive cells were increased with the postincubation more than 30 minutes in the range of 3-5%. This result suggested that the heavy ion irradiation induced bystander effect on the phosphorylation of histone H2AX in CHO-K1 cells.
