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 |
|---|---|
| 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 |
| Externally published | Yes |
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Keywords
- cell volume
- intracellular fluids
- nonlinear models
- paracellular pathway
- serosal potassium
- sodium transport
- tight epithelia
ASJC Scopus subject areas
- Physiology
- Cell Biology
- Biophysics
Cite this
Transepithelial Na+ transport and the intracellular fluids : A computer study. / Civan, Mortimer M.; Bookman, Richard J.
In: The Journal of Membrane Biology, Vol. 65, No. 1-2, 01.02.1982, p. 63-80.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Transepithelial Na+ transport and the intracellular fluids
T2 - A computer study
AU - Civan, Mortimer M.
AU - Bookman, Richard J.
PY - 1982/2/1
Y1 - 1982/2/1
N2 - 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.
AB - 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.
KW - cell volume
KW - intracellular fluids
KW - nonlinear models
KW - paracellular pathway
KW - serosal potassium
KW - sodium transport
KW - tight epithelia
UR - http://www.scopus.com/inward/record.url?scp=0020471826&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0020471826&partnerID=8YFLogxK
U2 - 10.1007/BF01870470
DO - 10.1007/BF01870470
M3 - Article
C2 - 7057462
AN - SCOPUS:0020471826
VL - 65
SP - 63
EP - 80
JO - Journal of Membrane Biology
JF - Journal of Membrane Biology
SN - 0022-2631
IS - 1-2
ER -