Role of TAT-system in cardiac excitability: investigation in a quantitative model of a ventricular cardiac cell
| Autoři | |
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| Rok publikování | 2002 |
| Druh | Konferenční abstrakty |
| Fakulta / Pracoviště MU | |
| Citace | |
| Popis | 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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