Voltage modulation of membrane permeability and energy utilization in cells

Abstract

Cell membranes are inherently electrical in nature. Charge movements across, and electric potentials experienced by membranes are used to process and transmit information, transduce energy, and perform other essential functions of a cell. Thus, the electrical properties of cell membranes are topics of study in nearly every branch of the biological sciences (1-6). This article will limit its scope to two recent developments using electric pulses, namely, (1) to implant pores of controlled size in cell membranes, and hence, to modify the permeability of the membrane; (2) to activate membranebound ATPases, and hence, to study the energy utilization process in cells. The use of electric pulses to induce cell alignments and fusions will also be briefly mentioned. It will focus on some basic findings and how this newly acquired knowledge may be further developed into useful tools for biological research. As such, a large portion of the material covered will be selected from our own experience. Readers interested in a broader aspect of the electrical properties of membranes, or in a survey of the literature in specific areas of research, should consult regular and more complete reviews (1-6). When a ceil in suspension is exposed to a voltage pulse, it experiences effects of an electric field and 3oule heating (7; Table 1). Electric field effects, such as electrophoresis of charged molecules or membrane proteins (8,9), orientation of ceils (10-12), and dissociation of molecules or complexes (13), are common to all chemical systems. However, because o5 the specific architecture of cells and membrane vesicles, all of these eifects may be amplified. This occurs when a spherical cell (radius a), made of membrane material much less conductive compared to the medium on both sides of the membrane, is exposed to an electric field, inducing a transmembrane potential, AO.