Abstract
Although linear non-threshold model is a basic theory for the regulation of radioprotection, the model does not consider irradiation time or dose rate. We have established Modified Exponential (MOE) model describing dose-rate effect of ionizing radiation, by measuring growth inhibition and micronucleus formation of human osteosarcoma, U2OS. Here, we applied MOE model to various kinds of cells other than U2OS cells to show generality of MOE model.
Cells were irradiated by culturing in the room bearing 50,000 Ci cobalt 60 as an irradiation source, further cultured for 48 h outside of the room, and pulsed with tritium thymidine for 4 h to evaluate growth inhibition. We observed that dose rate effect similar to U2OS in M059K, a human glioma, Jurkat and HL-60, human leukemias, or WI-38, a normal human fibroblast, and it followed to MOE model. In contrast, the dose rate effect was greatly impaired in the cell lines deficient of p53, DNA-PK or ATM. These results suggest that MOE model can be generally applied to vast variety of cell lines, ant that dose rate effect as described by MOE model is at least in part dependent on genes related to DNA repair.
