A General Relation between Membrane Potential, Ion Activities, and Pump Fluxes for Nonsymmetric Cells in a Steady State

In a previous paper Jacquez and Schultz [Math. Biosci. 20: 19 (1974)) derived a set of relations between the membrane potential, ion activities, ion permeabilities, and mediated ion fluxes which held for steady states of cells with plasma membranes that were everywhere the same. In this paper I show that similar relations hold for cells with plasma membranes that are nonuniform. These hold for steady states of polarized cells such as epithelial cells in suspension as well as for cells in epithelial membranes under short circuit conditions when the bathing solutions at the two faces have the same composition. INTRODUCTION In a previous paper Jacquez and Schultz [I] derived a set of general relations between the membrane potential, ion activities, ion permeabilities, and mediated ion fluxes which held for steady states of cells with uniform plasma membranes. The derivation depended on the steady state condition for each ion, i.e. that the net flux of each ion is zero. Among the many relations obtained, one of particular interest was the following, which had been derived previously under more restrictive conditions by Mullins and Noda [2]: