DNA DSB induction and rejoining in V79 cells irradiated with light ions: aconstant field gel electrophoresis study

Purpose: To study the induction and the time-course of rejoining of DNA dou ble strand breaks (DSB) in V79 cells irradiated with light ions with differ ent linear energy transfer (LET). Materials and methods: V79 cells were irradiated in monolayer with monoener getic proton, deuteron, helium-3 or helium-4 ion beams, each at two differe nt energy values. Gamma rays were used as reference radiation. DSB have bee n measured by constant field gel electrophoresis (CFGE). Results: The initial yield depended little on the particle type and LET. Th e amount of DSB left unrejoined For up to 2 h incubation time could be roug hly described by a decreasing exponential function with a final plateau, al though more complex functions cannot be excluded. Radiation quality had lit tle effect on the rejoining rate but affected the plateau. The amount of re sidual DSB after 2 h was higher for densely than for sparsely ionizing radi ation, and for the same particle was dependent on LET. The corresponding RB E ranged from 1.8 to 6.0. Conclusions: The results support the hypothesis that complex, less reparabl e DSB are induced in higher proportion by light ions with respect to gamma- rays and that, for the same ion, increasing LET leads to an increase in thi s proportion.