Effect of salt solutions on radiosensitivity of mammalian cells. III. Treatment with hypertonic solutions.

V79 Chinese hamster cells were treated with hypertonic solutions of NaCl or KCl and irradiated rat various times before, during, or after exposure to the solution. In solutions of molarities between 0-2 and 0-5 M, the cellular radiosensitivity increases with the molarity of the bathing solution. At these molarities, the hypertonic solution need not be present during irradiation to sensitize cells. Furthermore, radiosensitivity of cells could be increased by exposing cells for longer times to the hypertonic solution before irradiation. At higher salt concentrations (at 1-5 to 1-8 M), significant radioprotection is observed. Survival curve data showed that this protection was characterized by an increase in DO and a decrease in n, while the survival curves of cells sensitized with 0-465 M NaCl or with lower concentrations exhibited mainly changes in DO. The 1-55 M NaCl solution must be present during radiation to give a protective effect. Prolonged exposure to the salt before irradiation reduced the amount of radioprotection afforded by the salt. The results are discussed in terms of the effects of ions on histones, cellular water structure and the cell-aging cycle.