Regulation of Cell Volume by Nanosecond Pulsed Electric Fields

Stimulation of cells by nanosecond pulsed electric fields (nsPEFs) has attracted attention as a technology for medical applications such as cancer treatment. nsPEFs have been shown to affect intracellular environments without significant damage to cell membranes; however, the mechanism underlying the effect of nsPEFs on cells remains unclear. In this study, we constructed electrodes for applying nsPEFs and analyzed the change in volume of a single cell due to nsPEFs using fluorescence and Raman microscopy. It was shown that the direction of the change depended on the applied electric field; expansion due to the influx of water was observed at high electric field, and cell shrinkage was observed at low electric field. The change in cell volume was correlated to the change in the intracellular Ca²⁺ concentration, and nsPEFs-induced shrinking was not observed when the Ca²⁺-free medium was used. This result suggests that the cell shrinkage is related to the regulatory volume decrease where the cell adjusts the increase in intracellular Ca²⁺ concentration, inducing the efflux of ions and water from the cell.