EFFECT OF HYPERTHERMIA ON TRANSMEMBRANE POTENTIAL OF HELA-CELLS - A FLOW CYTOMETRIC ANALYSIS

The effect of hyperthermia on transmembrane potential was studied in H eLa cells in vitro using a 3',3'-dipentyl oxacarbocyanine [Di-O-C-5(3) ], a lipophilic cation probe that equilibrates across the plasma membr ane according to the transmembrane potential. Uptake of the fluorescen t probe was measured by flow cytometry. The fluorescent intensity (FT) increased with increase in temperature, and the increase was statisti cally significant when the duration of heat treatment was 30 minutes o r more. At each temperature studied the depolarization was higher afte r longer duration of heat treatment (p value: 41 degrees C < 0.05; 42 degrees C < 0.005; 43 degrees C < 0.001 and 44 degrees C < 0.001, resp ectively). The lack of significant depolarization after shorter durati on of heating, particularly at lower temperatures could be due to the repair of membrane damage that could have occurred in the holding inte rval between heating and measurement. The results suggest that depolar ization of membrane potential, i.e. increase in the intracellular cati on concentration, can be considered as an indicator of cell injury by hyperthermia and may be mechanistically related to cell death by heat treatment. The technique may be suitable for studying repair of damage after hyperthermia.