Interaction of sublethal and potentially lethal 450-hyperthermia and radiation damage at 0, 20, 37 or 400C

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 450C-hyperthermia damage and radiation damage on the survival of Chinese hamster ovary (CHO) cells was determined at temperatures of 0-40, 200 and 400C. Subphysiological temperatures inhibited to various degrees both the repair of sublethal radiation and sublethal 450C-hyperthermia damage while incubation at 400C apparently led to the conversion of sublethal 450C-hyperthermia lesions to lethal lesions. Potentially lethal hyperthermia damage (H-PLD) was repaired at 0-40 and 200C; whereas the repair of potentially lethal radiation damage (X-PLD) occurred at 200C, but not at 0-40 or 400C. The interaction of 450C-hyperthermia and radiation damage at temperatures of 0-40, 200 and 400C represented a super-position of the separate effects of the two treatment modalities separately combined with incubation at 0-40, 200 or 400C. This suggests that ionizing radiation and hyperthermia are affecting distinct targets and that H-PLD and X-PLD do not interact. (author)