title: The effect of hyperthermia on transmembrane potential in Chinese hamster ovary cells in vitro.
abstract: The effect of elevated temperature on transmembrane potential was studied in Chinese hamster ovary cells in vitro using tetraphenylphosphonium cation (TPP+) and 3,3'-dipentyloxacarbocyanine [Di-O-C5(3)], two unrelated lipophilic cation probes that equilibrate across the plasma membrane according to the transmembrane potential. Uptake of TPP+ was measured using a tritium-labeled probe and the uptake of the fluorescent probe Di-O-C5(3) was measured by flow cytometry. The Nernst equation was used to calculate transmembrane potential. The absolute values obtained for transmembrane potential at 37 degrees C using the two probes were different, but qualitatively similar results were obtained using either probe in the hyperthermia studies. Transmembrane potential measured at 43 and 45 degrees C was at least 20% higher than that measured at 37 degrees C, and the difference was statistically significant (P = 0.025 and P less than 0.01, respectively). The hyperpolarization induced by exposure to 45 degrees C persisted temporarily after cells had been returned to 37 degrees C. The hyperpolarization at 37 degrees C associated with a previous exposure to hyperthermia was maximal after cells had been held at 45 degrees C for 2.0 min, and fell to normal levels after 15.0 min at 37 degrees C.
authors.affiliation: Kingston Cancer Centre, Ontario, Canada.
authors.forename: C F
authors.initials: CF
authors.lastname: Quirt
authors.forename: W J
authors.initials: WJ
authors.lastname: Mackillop
mesh_terms: D000818:Animals; D002232:Carbocyanines; D006358:Hot Temperature; D007202:Indicators and Reagents; D008564:Membrane Potentials / Q000502:physiology*; D009861:Onium Compounds; D009943:Organophosphorus Compounds
chemical_list: D002232:Carbocyanines; D007202:Indicators and Reagents; D009861:Onium Compounds; D009943:Organophosphorus Compounds; C018528:3,3'-dipentyl-2,2'-oxacarbocyanine; C013289:tetraphenylphosphonium