Membrane surface potential in relation to a possible mechanism for intercellular interactions and cellular responses: A physical basis

Abstract

It is suggested that changes in the electrostatic potential of cell surface membranes in close proximity might occur simply as a result of the approach of charged surfaces in electrolytic media. If changes in surface potential were to initiate changes in membrane properties, modification of cellular behaviour in response to close apposition of cell surface membranes would be possible. Here a tentative physical basis indicating the feasibility of cell surface membrane electrostatic double layer interaction based on the Verwey-Overbeek theory of lyophobic colloid stability is put forward. The treatment differs from the latter in attempting to describe the interaction of biological membranes. For this reason, surface charges are considered to be fixed rather than reversibly adsorbed, and in consequence a model of interaction at constant surface charge but variable surface potential is obtained. It is shown that surface potential is a function of the distance separating charged membranes and as cells come into close contact (< 20 Å in physiological saline) their surface potentials undergo a local rise. This treatment is extended to the interaction of membranes bearing a superficial layer which is partially penetrable to solute ions, since there is reason to believe that at least some cell surfaces possess this property. In a wider context the possible importance of membrane surface potential is stressed and a general scheme of cellular responses is tentatively formulated wherein the primary action of diverse environmental effectors, including changes in ionic strength and molecular adsorption, is interpreted in terms of an alteration in membrane surface potential. This may induce conformational changes in membrane molecules, leading perhaps to a change in membrane permeability and cytoplasmic reaction to the modified intracellular ionic environment, resulting in characteristic cellular response. Membrane surface potential is thus envisaged as a transducer, mediating between environmental action and cellular reaction. Biological examples of specialized behaviour exhibited by cells which may be explicable in these terms will be examined in a subsequent paper.