Induction and reparation of double-strand DNA breaks in V79 cells continuously exposed to low dose-rate Y-radiation

Aim: to study the patterns of changes in the number of DNA double-strand breaks (DSB) in mammalian cells continuously exposed to low dose-rate y- radiation. Material and methods. Chinese hamster lung fibroblasts (V79) were used in this study. The y- irradiation of cells at a dose rate of 0.1 mGy/min was performed using the «Gamma-Panorama» unit (Cs-137). The fluorescence immunoassay of the phosphorylated H2AX-histone (y-H2AX) foci was used to investigate the DNA DSBs formation. Frequency of apoptotic cells was evaluated using «DNA halo» assay. 5 (6) — chloromethyl-2,7-dichlorodihydrofluorescein diacetate was used to estimate the reactive oxygen species (ROS) production. Results, it was showed that continuous low dose-rate irradiation of Chinese hamster V79 cells induces an increase of the y-H2AX foci number and ROS production rate at the early stages of exposure time (6-24 h, doses 3.6-14.4 cGy), while increasing exposition time and, therefore, the radiation dose (48-72 h, 28.8-43.2 cGy) caused a decrease in these endpoints to almost the control level. There was observed no significant changes in the frequency of apoptotic cells. Conclusion. It is assumed that the processes causing the DSB amount changes in mammalian cells continuously exposed to low dose-rate y-radiation are associated with the development of oxidative stress and subsequent activation of cellular antioxidant defense systems.