[Dependence of mice fibrobslasts radiosensitivity on the exposure conditions]

In the scientific literature there is lengthy discussion concerning utilization of low-dose hypersensitivity and bystander in radiation therapy which inspired us to investigate these effects using cells of mice fibroblasts C3H10T1/2. Irradiated were monolayers of fibroblasts cells cultivated on wall of plastic vials. To study the bystander effect, the therapeutic proton beam with the onset energy of 150 Me V was directed at the whole wall (25 cr2) or only the central area of 1 cv(2). In an hour after irradiation the cells were dispersed in 0.25 % tripsin solution and inoculated in vials for survivability analysis. In both cases survivability of the cells was essentially equal following irradiation by 0.5 Gy, 2 Gy and 5 Gy. The same observation was made also after fractionated irradiation by the total doses of 10 and 20 Gy (2 Gy per a day, 5 times a week). In these experiments, each time another area (1 cm(2)) of the vial wall was subjected to irradiation. Three 0.4 Gy fractionated irradiations of cells C3H10OT1/2 per a day (5 times a week) by gamma-source 60Co with an interval of 3 hours showed that the total dose of 6 Gy and 12 Gy gathered by this protocol had the strongest lethal effect on fibroblast cells as compared with the daily one-time irradiation by 1.2 Gy. According to these results, detail studies of the low-dose hypersensitivity and bystander effects may come up with their effective utilization in radiation therapy.