Influence of hyperthermia, pH and culturing conditions on the electrical parameters of Chinese hamster V79 cells

Conductivity measurements in the frequency range 10 kHz-100 MHz have been performed on Chinese hamster fibroblasts V79 exposed to hyperthermia in different experimental conditions. The membrane electrical conductivity is decreased when cells are heated for 1 h at 44 degrees C or 3 h at 43 degrees C at pH 7.25. This effect has not been observed on cell samples following heating for 1 h at 43 degrees C at pH 7.25. However, if the pH of the culture medium is adjusted to 6.50 or 6.0 before hyperthermic exposure, a substantial decrease of membrane conductivity is observed. In cells maintained in partially spent medium before heating, a 3 h treatment at 43 degrees C at pH 7.25 does not produce any effect on membrane conductivity. The results of all these experiments seem to indicate that some alteration of the energy-driven mechanisms involved in active transport across the plasma membranes may be responsible for the observed effects.