Fixation of radiation-induced potentially lethal damage by anisotonic treatment and its modification by DMSO or BrdUrd in V79 cells.

The effects of radiosensitization by bromodeoxyuridine (BrdUrd) substitution and radioprotection by dimethyl sulfoxide (DMSO) have been examined in relation to fixation and repair of radiation damage by anisotonic treatment. The fixation of radiation damage in cells exposed to 0.05 M or 1.5 M NaCl after irradiation was the same at equal survival levels irrespective of (BrdUrd) incorporation into the DNA. Also, during incubation between irradiation and a subsequent anisotonic treatment, cells containing BrdUrd repaired radiation damage to the same extents as cells without BrdUrd. DMSO treatment resulted in radioprotection. Fixation, by anisotonic salt treatment, of damage resulting from irradiation in the presence of DMSO was less extensive than from irradiation in the absence of DMSO, even though X-ray doses were adjusted to give equal survival levels. Recovery during incubation at 37 degrees C between irradiation and a subsequent salt treatment occurred for irradiation in the presence and absence of DMSO. These data show that the alteration of DNA radiosensitivity by BrdUrd had no effect on fixation or repair of radiation damage as assessed by salt treatment, while DMSO which is an OH scavenger caused the damage to be less susceptible to fixation and this damage was repaired during incubation at 37 degrees C.