Enhancement of X-ray induced potentially lethal damage by low temperature storage of mammalian cells

Studies have been made of the effect of periods of storage at 40C on V79 Chinese hamster fibroblasts after X-irradiation (0 to 1100 rad) at 40C. This cold storage caused a continuous biphasic decrease in survival with time, the effect increasing with the initial dose. The initial decrease was rapid and followed by a slower decrease after two to six hours. The survival of the unirradiated control cells stored at 40C was unchanged over the 30 hour period of the experiments. If the cells were warmed to room temperature or 370C for as little as ten minutes after irradiation, or even if the cells were irradiated at these higher temperatures, no subsequent decrease in survival was caused by storage at 40C. This effect implies that whatever agent is responsible for the synergistic killing has a very short half-life at higher temperatures. Consideration is given to possible explanations for the conflicting reports in the literature. (U.K.)