Electrogenic properties of the sodium pump in a dynamic model of membrane transport.

Abstract

The general purpose of this theoretical work is to contribute to understand the physiological role of the electrogenic properties of the sodium pump, by studying a dynamic model that integrates diverse processes of ionic and water transport across the plasma membrane. For this purpose, we employ a mathematical model that describes the rate of change of the intracellular concentrations of Na+, K+ and Cl-, of the cell volume, and of the plasma membrane potential (Vm). We consider the case of a nonexcitable, nonpolarized cell expressing the sodium pump; Na+, K+, Cl- and water channels, and cotransporters of KCl and NaCl in its plasma membrane. We particularly analyze here the conditions under which the physiological Vm can be generated in a predominantly electrogenic fashion, as a result of the activity of the sodium pump. A major conclusion of this study is that, for the cell model considered, a low potassium permeability is not a sufficient condition for a predominantly electrogenic generation of the Vm by the sodium pump. The presence of an electroneutral exchange of Na+ and K+ represents a necessary additional requirement.