Ionic-strength modulation of electrically induced permeabilization and associated fusion of mammalian cells

Application of a high electric field to cells in culture has been shown to make them both permeable and fusogenic. The molecular events involved in the phenomenon are still poorly understood. In this study we investigated the effects of the ionic strength of the pulsing buffer on the electropermeabilization and electrofusion of Chinese hamster ovary cells. Increasing the ionic strength of the pulsing medium results in an increase in sieving of transient permeant structures, but decreases the fusion index. Treatment of cells with trypsin or pronase before application of the pulses abolishes the ionic modulation of both electropermeabilization and electrofusion. A similar rate of expansion of permeabilization is obtained whatever the ionic content of the pulsing buffer, and cells fuse even at high ionic strength. This observation lends support to our hypothesis that membrane proteins play a role in electrofusion.