Repair following combined X-ray and heat at 41 degrees in plateau-phase mammalian cells.

Plateau-phase V79 Chinese hamster cells maintained at 37 degrees following X-irradiation demonstrated both sublethal damage repair and potentially lethal damage repair. When cells were kept at 41 degrees for 1 hr following irradiation, no sublethal damage repair was seen. In contrast, irradiated cells maintained at 41 degrees for 1 hr and then returned to 37 degrees were capable of repairing both sublethal and potentially lethal radiation damage; hyperthermic (41 degrees) inhibition of radiation damage repair was reversible. Repair was similar for cells heated before or after irradiation. The extent of sublethal damage repair (as measured by recovery ratios and quasi-threshold doses) and potentially lethal damage repair (as measured by recovery ratios and dose-modifying factors) was similar following combined heat and X-ray treatment and following X-ray treatment alone.