Repair of potentially mutagenic damage and radiation quality

The induction of potentially lethal damage and potentially mutagenic damage expressed by hypertonic salt treatment in late S-phase V79 cells after exposure to 46-MeV fast neutrons and 50-kVp X rays has been studied. Resistance to 6-thioguanine was used as the mutagenic end point. When cells in late S phase were treated with hypertonic salt solution immediately after fast neutrons or X irradiation, both cell killing and mutation induction were enhanced compared to fast neutrons or X irradiation alone. These results suggest that neutron as well as X irradiation of cells in late S phase induces both potentially lethal damage and potentially mutagenic damage. However, some differences in mutation frequency were observed between the two radiations after salt treatments. These results are discussed in terms of repair of mutagenic damage by an error-free or error-prone process.