Use of a radical scavenger to study DSB induction and repair in V79 mammalian cells exposed to neutrons from a 252-CF source

Dimethyl Sulfoxide (DMSO) was used as a radical scavenger to study the direct and indirect effects of neutron irradiation on cellular inactivation, double strand break (dsb) induction and repair of V79-4 mammalian cells exposed to the californium source. Preliminary results suggest that for cellular inactivation the neutrons give a RBE of 2.3 at 10 % survival level. The use of 0.75 mol dm-3 DMSO gives a protection factor of 1.2 for cell inactivation. For initial induction of dsb irradiated at 4 deg. C, measured by pulsed field gel electrophoresis (PFGE), the RBE was found to be 1.0, the presence of DMSO reduced the initial yield by 50 %. If the dsb induced are allowed to repair at 37 deg C for up to 16 hours, after 1 hour approximately 50 %. If the dsb induced are allowed to repair at 37 deg C for up to 16 hours, after 1 hour approximately 50 % of these lesions were rejoined, in the presence of DMSO there was insignificant repair after this time. At the longer repair time, most of the dsb rejoined in both cases. These findings confirm that high LET particles are more effective than low LET photons at cellular inactivation and DSMO protects against radical damage that the cell is able to repair. As with high LET α-particles, the non-scavengeable dsb are not readily rejoined at short times. (authors)