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.
D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D006863:Hydrogen-Ion Concentration; D006979:Hyperthermia, Induced; D000860:Hypoxia / Q000503:physiopathology*; D066298:In Vitro Techniques; D051379:Mice; D008806:Mice, Inbred AKR; D009374:Neoplasms, Experimental / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy; D010954:Plasmacytoma / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D011879:Radiotherapy Dosage; D014964:X-Ray Therapy