Hyperthermia in a differentiating murine erythroleukaemia cell line: II. Effect of heat on haem induction by radiation.

Friend erythroleukaemia cells (FELC) were induced to a haem-producing state by X-rays. The percentage of haem positive cells was maximum for doses between 10 and 15 Gy. Heat treatment at 42.0 degrees C or 45.0 degrees C during or after irradiation inhibited haem induction whereas heating before irradiation enhanced it. Incubation at 37 degrees C between heating and irradiation resulted in a decline in induction levels, indicating repair of heat damage that interacts with X-ray damage. Incubation at 37 degrees C between irradiation and heating did not result in changed haem induction levels, indicating a lack of repair of radiation damage that could interact with subsequent damage produced by heating.