Electrogenic Properties of the Sodium Pump in a Dynamic Model of Membrane Transport |
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Authors: | JA Hernández S Chifflet |
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Institution: | (1) Sección Biofísica, Facultad de Ciencias, Univ. de la República, Iguá esq. Mataojo, 11400 Montevideo, Uruguay, UY;(2) Depto. de Bioquímica, Facultad de Medicina, Univ. de la República, Gral. Flores 2125, 11800 Montevideo, Uruguay, UY |
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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 (V
m
). 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 V
m
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 V
m
by the sodium pump. The presence of an electroneutral exchange of Na+ and K+ represents a necessary additional requirement.
Received: 8 September 1999/Revised: 21 March 2000 |
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Keywords: | : Sodium pump — Electrogenic enzymes — Membrane potential — Mathematical models |
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