Transepithelial Na+ transport and the intracellular fluids: A computer study

Mortimer M. Civan, Richard J. Bookman

19 Scopus citations

Abstract

Computer simulations of tight epithelia under three experimental conditions have been carried out, using the rheogenic nonlinear model of Lew, Ferreira and Moura (Proc. Roy. Soc. London. B206:53-83, 1979) based largely on the formulation of Koefoed-Johnsen and Ussing (Acta Physiol. Scand. 42:298-308, 1958). First, analysis of the transition between the short-circuited and open-circuited states has indicated that (i) apical Cl- permeability is a critical parameter requiring experimental definition in order to analyze cell volume regulation, and (ii) contrary to certain experimental reports, intracellular Na+ concentration (cNac) is expected to be a strong function of transepithelial clamping voltage. Second, analysis of the effects of lowering serosal K+ concentration (cKs) indicates that the basic model cannot simulate several well-documented observations; these defects can be overcome, at least qualitatively, by modifying the model to take account of the negative feedback interaction likely to exist between the apical Na+ permeability and cNac. Third, analysis of the effects induced by lowering mucosal Na+ concentration (cNam) strongly supports the concept that osmotically induced permeability changes in the apical intercellular junctions play a physiological role in conserving the body's stores of NaCl. The analyses also demonstrate that the importance of Na+ entry across the basolateral membrane is strongly dependent upon transepithelial potential, cNam and cKs; under certain conditions, net Na+ entry could be appreciably greater across the basolateral than across the apical membrane.

Original languageEnglish
Pages (from-to)63-80
Number of pages18
JournalThe Journal of Membrane Biology
Volume65
Issue number1-2
DOIs
StatePublished - Feb 1 1982
Externally publishedYes

Keywords

  • cell volume
  • intracellular fluids
  • nonlinear models
  • paracellular pathway
  • serosal potassium
  • sodium transport
  • tight epithelia

ASJC Scopus subject areas

  • Physiology
  • Cell Biology
  • Biophysics

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