A Study of the Repair of Potentially Lethal and Sublethal Radiation Damage in Chinese Hamster Cells Exposed to Extremely Hypo- or Hypertonic NaCl Solutions

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Abstract
The effect of 0.05 and 1.5 M NaCl solutions on the repair of potentially lethal damage (PLD) and sublethal damage (SLD) in irradiated Chinese hamster ovary (CHO) cells was examined. A 20 min exposure to the 0.05 or 1.5 M salt solutions which was terminated immediately before irradiation had no effect on the repair of PLD. Salt treatment during or after irradiation caused an inhibition of repair of PLD. The possibility that 0.05 or 1.5 M treatment irreversibly affected repair enzymes could be ruled out. Exposure of cells to 0.05 or 1.5 M NaCl solutions before or during the first X-ray dose of a split-dose regimen decreased the ability of the cell to repair SLD. The recovery observed in the experiments was characterized by a change in Do [mean lethal dose] of the survival curves and was related to the loss of interaction of radiation-induced lesions and salt effects as the incubation time between the 2nd X-ray dose and salt treatment increased. A partial return of the shoulder of the survival curve when salt treatment preceded split-dose irradiation indicated that some repair of SLD occurs. Salt treatment prior to irradiation does not inhibit repair of SLD or PLD but salt treatment during or after irradiation inhibits repair of both SLD and PLD.