Modeling electroporation in a single cell. I. Effects of field strength and rest potential

This study develops a model for a single cell electroporated by an external electric field and uses it to investigate the effects of shock strength an d rest potential on the transmembrane potential V-m and pore density N arou nd the cell. As compared to the induced potential predicted by resistive-ca pacitive theory, the model of electroporation predicts a smaller magnitude of V-m throughout the cell. Both V-m and N are symmetric about the equator with the same Value at both poles of the cell. Larger shocks do not increas e the maximum magnitude of V-m because more pores form to shunt the excess stimulus current across the membrane. In addition, the value of the rest po tential does not affect V-m around the cell because the electroporation cur rent is several orders of magnitude larger than the ionic current that supp orts the rest potential. Once the field is removed, the shock-induced V-m d ischarges within 2 mu s, but the pores persist in the membrane for several seconds. Complete resealing to preshock conditions requires approximately 2 0 s. These results agree qualitatively and quantitatively with the experime ntal data reported by Kinosita and coworkers for unfertilized sea urchin eg gs exposed to large electric fields.