- Author:
- Catherine Lloyd <c.lloyd@auckland.ac.nz>
- Date:
- 2010-04-20 12:38:43+12:00
- Desc:
- Added image files (taken from Gross 1999 workspace) and added documentation and metadata. The model curation status comment needs to be added.
- Permanent Source URI:
- http://models.cellml.org/workspace/gross_and_hopfer_1998/rawfile/0c5306c5dc251852cc1a1116f015fc54f543161a/gross_and_hopfer_1998.cellml
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This CellML file was generated on 28/08/2009 at 1:20:47 at p.m. using:
COR (0.9.31.1265)
Copyright 2002-2009 Dr Alan Garny
http://COR.physiol.ox.ac.uk/ - COR@physiol.ox.ac.uk
CellML 1.0 was used to generate this model
http://www.CellML.org/
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<title>Voltage and cosubstrate dependence of the Na-HCO3 cotransporter kinetics in renal proximal tubule cellse</title>
<author>
<firstname>Jonna</firstname>
<surname>Terkildsen</surname>
<affiliation>
<shortaffil>Auckland Bioengineering Institute, University of Auckland</shortaffil>
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This CellML model..........................................
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<title>Model Structure</title>
<para>
ABSTRACT: The voltage dependence of the kinetics of the sodium bicarbonate cotransporter was studied in proximal tubule cells. This electrogenic cotransporter transports one Na+, three HCO3-, and two negative charges. Cells were grown to confluence on a permeable support, mounted on a Ussing-type chamber, and permeabilized apically to small monovalent ions with amphotericin B. The steady-state, di-nitro-stilbene-di-sulfonate-sensitive current was shown to be sodium and bicarbonate dependent and therefore was taken as flux through the cotransporter. Voltage-current relations were measured as a function of Na+ and HCO3- concentrations between -160 and +160 mV under zero-trans and symmetrical conditions. The kinetics could be described by a Michaelis-Menten behavior with a Hill coefficient of 3 for HCO3- and 1 for Na+. The data were fitted to six-state ordered binding models without restrictions with respect to the rate-limiting step. All ordered models could quantitatively account for the observed current-voltage relationships and the transinhibition by high bicarbonate concentration. The models indicate that 1) the unloaded transporter carries a positive charge; 2) the binding of cytosolic bicarbonate to the transporter "senses" 12% of the electric field in the membrane, whereas its translocation across the membrane "senses" 88% of the field; 3) the binding of Na+ to the cotransporter is voltage independent.
</para>
<para>
The original paper reference is cited below:
</para>
<para>
Voltage and cosubstrate dependence of the Na-HCO3 cotransporter kinetics in renal proximal tubule cellse, E. Gross and U. Hopfer, 1998,
<emphasis>Biophysical Journal</emphasis>, 75, 810-824. <ulink url="http://www.ncbi.nlm.nih.gov/pubmed/9675182">PubMed ID: 9675182</ulink>
</para>
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<caption>A six-state ordered-binding transport model of the Na-HCO3 cotransporter. The binding of three HCO3- anions to the carrier is described as a single, lumped step.</caption>
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Voltage and cosubstrate dependence of the Na-HCO3 cotransporter kinetics in renal proximal tubule cellse
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