Responses to hyperthermia (42.DEG.,44.DEG.) and/or radiation in four mammalian cell lines in vitro.

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Abstract
Survival in response to hyperthermia at 42 and 44°C, both alone and in combination with X-irradiation was examined in vitro in Chinese hamster V-79, HeLa-S3, murine Ehrlich ascites tumor cells (EH) and murine L-fibroblasts. L-cells were markedly thermo and radiosensitive, while the other three cell lines, although not so sensitive did show similar responses. When each cell line was exposed to split dose Hyperthermia in the 42→44°C sequence, survival after the second treatment was increased for V-79 and HeLa-S3 cells, but was not significantly changed for EH and L-cells. In the case of split dose exposure in the 44→42°C sequence, survival after the second treatment was markedly decreased for V-79, EH and HeLa-S3 cells, but only slightly for L-cells. When hyperthermia at 42 or 44°C was followed by X-irradiation immediately, V-79, EH and HeLaS3 cells showed decrements in both Dq and Do values, while L-cells showed a decrement only in Dq but no significant change in Do. From these results, it seems that the hyperthermic damage by exposure to 44°C may be different from that by exposure to 42°C.