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 language | English (US) |
---|---|
Pages (from-to) | 63-80 |
Number of pages | 18 |
Journal | The Journal of Membrane Biology |
Volume | 65 |
Issue number | 1-2 |
DOIs | |
State | Published - Feb 1 1982 |
Keywords
- cell volume
- intracellular fluids
- nonlinear models
- paracellular pathway
- serosal potassium
- sodium transport
- tight epithelia
ASJC Scopus subject areas
- Physiology
- Cell Biology
- Biophysics