The influence of hypoxia and acidity on the hyperthermic response of malignant cells in vitro.
Colony formation of JB-1-E tumor cells was studied after hyperthermic treatment (42.5 degrees C) at a pH of 6.4 or 7.2 under hypoxic and euoxic conditions. At a pH of 7.2 and normal oxygen tension, there was a moderate decrease in colony formation with increasing duration of hyperthermic treatment (To = 65 min.). This effect was slightly enhanced under hypoxic conditions (To = 36 min.). The hyperthermic effect was enhanced to a considerably greater degree when treatment was performed at a pH of 6.4 (To = 19 min.), with no observable difference between hypoxia and euoxia. These findings indicate that environmental acidity is a determining factor in the hyperthermic effect. The hypoxic effect at a pH of 7.2 is probably due to a slight decrease in the intracellular pH caused by increased production of lactic acid.
The influence of hypoxia and acidity on the hyperthermic response of malignant cells in vitro. Colony formation of JB-1-E tumor cells was studied after hyperthermic treatment (42.5 degrees C) at a pH of 6.4 or 7.2 under hypoxic and euoxic conditions. At a pH of 7.2 and normal oxygen tension, there was a moderate decrease in colony formation with increasing duration of hyperthermic treatment (To = 65 min.). This effect was slightly enhanced under hypoxic conditions (To = 36 min.). The hyperthermic effect was enhanced to a considerably greater degree when treatment was performed at a pH of 6.4 (To = 19 min.), with no observable difference between hypoxia and euoxia. These findings indicate that environmental acidity is a determining factor in the hyperthermic effect. The hypoxic effect at a pH of 7.2 is probably due to a slight decrease in the intracellular pH caused by increased production of lactic acid.