Fixation of Potentially Lethal Radiation Damage by Post-irradiation Exposure of Chinese Hamster Cells to 0·5 M or 1·5 M NaCl Solutions

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Abstract
The effect of 0.05 and 1.5 M NaCl treatments on CHO [Chinese hamster ovary] cells during and after irradiation was examined. Treatment with hypotonic or hypertonic salt solutions during and after irradiation resulted in the fixation of radiation damage which would otherwise not be expressed. The half time for fixation was 4-5 min. The increased expression of the potentially lethal damage by anisotonic solutions was mainly characterized by large decreases in the shoulder of the survival curve and decreases in D0 [mean lethal dose]. Fixation of radiation damage at 37.degree. C occurred to a much greater extent for the hypertonic treatment than for the hypotonic treatment and was greater at 37.degree. than at 20.degree. C. The hypotonic and hypertonic treatments during and after irradiation reduced or eliminated the repair of sublethal and potentially lethal damage, treatment during irradiation only, radiosensitized the cells when the treatment was hypotonic and radioprotected the cells when the treatment was hypertonic. Salt treatments and different temperatures altering competition between repair and fixation of potentially lethal lesions were discussed. The number of lesions depends on the particular salt treatment at the time of irradiation.