A quantitative model of the cardiac ventricular cell incorporating the transverse-axial tubular system.
The role of the transverse-axial tubular system (TATS) in electrical activity of cardiac cells has not been investigated quantitatively. In this study a mathematical model including the TATS and differential distribution of ionic transfer mechanisms in peripheral and tubular membranes was described. A model of ventricular cardiac cell described by Jafri et al. (1998) was adopted and slightly modified to describe ionic currents and Ca2+ handling. Changes of concentrations in the lumen of the TATS were computed from the total of transmembrane ionic fluxes and ionic exchanges with the pericellular medium. Long-term stability of the model was attained at rest and under regular stimulation. Depletion of Ca2+ by 12.8% and accumulation of K+ by 4.7% occurred in the TATS-lumen at physiological conditions and at a stimulation frequency of 1 Hz. The changes were transient and subsided on repolarization within 800 ms (Ca2+) and 300 ms (K+). Nevertheless, the course of action potentials remained virtually unaltered. Simulations of voltage clamp experiments demonstrated that variations in tubular ionic concentrations were detectable as modulation of the recorded membrane currents.
Institute of Thermomechanics, Czech Academy of Sciences, Branch Brno, Czech Republic. pasek@umtn.fme.vutbr.cz
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Pásek
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Christé
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Simurda
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002462:Cell Membrane / Q000502:physiology*; D003198:Computer Simulation; D004558:Electric Stimulation; D006352:Heart Ventricles / Q000648:ultrastructure; D006801:Humans; D008955:Models, Cardiovascular; D032383:Myocytes, Cardiac / Q000502:physiology* / Q000648:ultrastructure; D012519:Sarcoplasmic Reticulum / Q000502:physiology*; D016276:Ventricular Function