INTERACTION OF SUBLETHAL AND POTENTIALLY LETHAL 45-DEGREES-C HYPERTHERMIA AND RADIATION-DAMAGE AT 0, 20, 37 OR 40-DEGREES-C

The interaction of hyperthermia damage and radiation damage has most often been studied under conditions which favoured repair of sublethal damage. In the present study the interaction of 45°C-hyperthermia damage and radiation damage on the survival of Chinese hamster ovary (CHO) cells was determined at temperatures of 0-4°, 20° and 40°C. Subphysiological temperatures inhibited to various degrees both the repair of sublethal radiation and sublethal 45°C-hyperthermia damage while incubation at 40°C apparently led to the conversion of sublethal 45°C-hyperthermia lesions to lethal lesions. Potentially lethal hyperthermia damage (H-PLD) was repaired at 0-4° and 20°C; whereas the repair of potentially lethal radiation damage (X-PLD) occurred at 20°C, but not at 0-4° or 40°C. The interaction of 45°C-hyperthermia and radiation damage at temperatures of 0-4°, 20° and 40°C represented a super-position of the separate effects of the two treatment modalities separately combined with incubation at 0-4°, 20° or 40°C. This suggests that ionizing radiation and hyperthermia are affecting distinct targets and that H-PLD and X-PLD do not interact. © 1979.