Role of TAT-system in cardiac excitability: investigation in a quantitative model of a ventricular cardiac cell

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Authors

PÁSEK Michal CHRISTÉ Georges. ŠIMURDA Jiří

Year of publication 2002
Type Conference abstract
MU Faculty or unit

Faculty of Medicine

Citation
Description To explore the effect of the cardiac transverse axial tubular system (TAT-system) on excitability of ventricular cells, we developed a quantitative model incorporating the function of the tubules. The model was based on a modified quantitative description proposed by Luo and Rudy (Circ Res, 1994;74:1071-96). The modifications are summarized in our previous publication (Pásek M. et al. Scripta Medica, 2002;75:179-86). The morphological parameters of the TAT-system were based on the study of Soeller and Cannel (Circ Res, 1999;84:266-75). The time constants of ionic diffusion between the TAT-system and external solution was set to 250 ms for Ca2+ ions and 63 ms for K+ and Na+ ions. The properties of the tubular and peripheral membrane were set according to recently published data. The results of simulations were strongly affected by incorporation of the TAT-system under the conditions of low external [K+]. The model including TAT-system began to produce early after-depolarizations at considerably lower values of external [K+] (1.8 mM at 1 Hz and 1.5 mM at 2 Hz) than the model without TAT-system (2.2 mM at 1 Hz and 1.9 mM at 2 Hz). Its higher stability resulted from higher level of tubular [K+] (versus low external [K+]) that sustained the activation of tubular K-conductances responsible for action potential repolarization and resting voltage. The main transporter underlying the higher level of tubular [K+] was an energy-dependent K+-pump that had to be included into the model to maintain potassium homeostasis. The results predict that the TAT-system may play a significant protective role against cellular arrhythmogenesis.
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