Sensitivity of transmembrane voltage induced by applied electric fields - a theoretical analysis

The sensitivity of induced transmembrane voltage to extracellular conductivity, membrane conductivity, cytoplasmic conductivity, cell radius and electric pulse duration has been studied. The study showed that variations of membrane conductivity, cytoplasmic conductivity and cell radius within the ranges of their physiological values do not influence induced transmembrane voltage substantially, provided that extracellular conductivity also corresponds to the physiological conditions, and duration of the electric pulse is in range of 10 mu s or longer. However, when extracellular conductivity is reduced to the values typical for a ''low conductivity'' medium, the induced transmembrane voltage decreases considerably, while the charging time of the membrane increases up to the range of 1 ms. This increases the necessary amplitude and duration of electric pulses used for electroporation. In a ''low conductivity'' medium, the induced transmembrane voltage is also much more sensitive to variations in cell radius, membrane conductivity, and cytoplasmic conductivity. Such a medium is used in many in vitro studies of the effects of an electric field upon single cells. Our study shows that in these cases, in order to evaluate the induced transmembrane voltage, it is important to consider the values of conductivities and radii of cells used in the experiment, as well as the duration of the electric pulses used. (C) 1997 Elsevier Science S.A.