Potentially lethal and DNA radiation damage: similarities in inhibition of repair by medium containing D2O and by hypertonic buffer

Killing of log-phase V79 Chinese hamster cells by ionizing radiation is enhanced when cells are treated immediately after irradiation with anisotonic phosphate-buffered saline or with medium containing 90% D2O. These treatments are not toxic to unirradiated cells. In medium containing D2O, cells are unable to repair sublethal damage; however, repair occurs after a shift to normal medium. Thus, as is observed with anisotonic buffer, enhanced killing by medium containing D2O does not prevent cells from repairing sublethal damage. Further aspects of the enhanced expression of potentially lethal damage by medium containing D2O and by anisotonic buffer are also similar. For example, both are largely ineffective after treatments involving nonionizing radiation, and both treatments retard the repair of DNA breaks. From the foregoing, and the partial overlapping of enhanced killing due to medium containing D2O and due to hypertonic saline, we infer that the latter treatments affect the repair, or reparability, of the same sensitive targets