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  • Title: The effect of hyperthermia on transmembrane potential in Chinese hamster ovary cells in vitro.
    Author: Quirt CF, Mackillop WJ.
    Journal: Radiat Res; 1991 Apr; 126(1):96-103. PubMed ID: 2020742.
    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.
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