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A model of the guinea-pig ventricular cardiac myocyte incorporating a transverse-axial tubular system
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Model Documentation
Model Status
This CellML model is known to run in both COR and PCEnv and the CellML is valid and error free. The units have been checked and they are consistent. However, the model does not yet recreate the published results. We are continuing to curate this CellML model in an attempt to get it to mimic the original published model. This particular translation was based on the published paper alone.
Model Structure
ABSTRACT: A model of the guinea-pig cardiac ventricular myocyte has been developed that includes a representation of the transverse-axial tubular system (TATS), including heterogeneous distribution of ion flux pathways between the surface and tubular membranes. The model reproduces frequency-dependent changes of action potential shape and intracellular ion concentrations and can replicate experimental data showing ion diffusion between the tubular lumen and external solution in guinea-pig myocytes. The model is stable at rest and during activity and returns to rested state after perturbation. Theoretical analysis and model simulations show that, due to tight electrical coupling, tubular and surface membranes behave as a homogeneous whole during voltage and current clamp (maximum difference 0.9 mV at peak tubular INa of -38 nA). However, during action potentials, restricted diffusion and ionic currents in TATS cause depletion of tubular Ca2+ and accumulation of tubular K+ (up to -19.8% and +3.4%, respectively, of bulk extracellular values, at 6 Hz). These changes, in turn, decrease ion fluxes across the TATS membrane and decrease sarcoplasmic reticulum (SR) Ca2+ load. Thus, the TATS plays a potentially important role in modulating the function of guinea-pig ventricular myocyte in physiological conditions.
The complete original paper reference is cited below:
A model of the guinea-pig ventricular cardiac myocyte incorporating a transverse-axial tubular system, Michal Pasek, Jiri Simurda, Clive H. Orchard, and Georges Christe, 2008, Progress in Biophysics and Molecular Biology , 96, 258-280. (Full text and PDF versions of the article are available for journal subscribers on the Progress in Biophysics and Molecular Biology website.) PubMed ID: 17888503
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| Schematic diagram of the ventricular cell model. The description of electrical activity of the surface (s) and tubular (t) membranes comprises formulation of the ion transporters shown. The intracellular space contains the subspace, the Ca2+-network (NSR) and junctional (JSR) compartments of sarcoplasmic reticulum and the Ca2+ buffers calmodulin (Bcm), troponin (Bhtrpn, Bltrpn) and calsequestrin (Bcs). The small filled rectangles in JSR membrane represent ryanodine receptors. The small bi-directional arrows denote Ca2+ diffusion. Ion diffusion between the tubular and the extracellular space is represented by the dashed arrow. |