STUDY OF THE REPAIR OF POTENTIALLY LETHAL AND SUBLETHAL RADIATION-DAMAGE IN CHINESE-HAMSTER CELLS EXPOSED TO EXTREMELY HYPOTONIC OR HYPERTONIC NACL SOLUTIONS

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 has been 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. However, salt treatment during or after irradiation caused an inhibition of repair of PLD. The possibiity 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 D0 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 second X-ray dose and salt treatment increased. However, a partial return of the shoulder of the survival curve when salt treatment preceded split-dose irradiation indicated that some repair of SLD does occur. In summary, salt treatment prior to irradiation does not inhibit repair of either SLD or PLD, whereas salt treatment during or after irradiation inhibits repair of both SLD and PLD.