A potential pitfall in the use of electroporation: cellular radiosensitization by pulsed high-voltage electric fields.

Chinese hamster ovary cells have been exposed to high-voltage electric fields causing electroporation (EP) and the interaction between EP and radiation-induced cell lethality investigated. There was a voltage-dependent decrease in plating efficiency, assessed immediately following EP, and cell viability, assessed at 24 h. A linear decrease was seen for both. These decreases were accompanied by a voltage-dependent increase in cell volume, assessed immediately following EP. A good correlation between increases in cell volume and decreases in plating efficiency was seen (r = -0.91). The application of electric fields immediately prior to, or following, irradiation led to a radiosensitization of the cells. This radiosensitization still occurred when a 6 h interval was left between radiation and EP but was lost when cells were irradiated 24 h prior to EP. When cells were irradiated following EP, the radiosensitization was lost with a 1 h interval between the two treatments. These results suggest that, when studying the combined cellular effects of EP of macromolecules and radiation, care should be taken that sufficient time has elapsed between the two modalities to prevent the radiosensitization of cells.