Pásek M, Simurda J, Christé G, Orchard C H
Institute of Thermomechanics, Czech Academy of Science, Branch Brno, Brno, Czech Republic.
Prog Biophys Mol Biol. 2008 Jan-Apr;96(1-3):226-43. doi: 10.1016/j.pbiomolbio.2007.07.021. Epub 2007 Aug 11.
The transverse-axial tubular system (TATS) of cardiac ventricular myocytes is a complex network of tubules that arises as invaginations of the surface membrane; it appears to form a specialised region of cell membrane that is particularly important for excitation-contraction coupling. However, much remains unknown about the structure and role of the TATS. In this brief review we use experimental data and computer modelling to address the following key questions: (i) What fraction of the cell membrane is within the TATS? (ii) Is the composition of the TATS membrane the same as the surface membrane? (iii) How good is electrical coupling between the surface and TATS membranes? (iv) What fraction of each current is within the TATS? (v) How important is the complex structure of the TATS network? (vi) What is the effect of current inhomogeneity on lumenal ion concentrations? (vii) Does the TATS contribute to the functional changes observed in heart failure? Although there are many areas in which experimental evidence is lacking, computer models provide a method to assess and predict the possible function of the TATS; such models suggest that although the surface and TATS membranes are electrically well coupled, concentration of ion flux pathways within the TATS, coupled to restricted diffusion, may result in the ionic composition in the TATS lumen being different from that in the bulk extracellular space, and varying with activity and in pathological conditions.
心肌心室肌细胞的横向-轴向管状系统（TATS）是一个由小管组成的复杂网络，它由表面膜内陷形成；它似乎形成了细胞膜的一个特殊区域，对兴奋-收缩偶联尤为重要。然而，关于TATS的结构和作用仍有许多未知之处。在这篇简短的综述中，我们利用实验数据和计算机建模来解决以下关键问题：（i）细胞膜有多少比例在TATS内？（ii）TATS膜的组成与表面膜相同吗？（iii）表面膜和TATS膜之间的电偶联有多好？（iv）每种电流有多少比例在TATS内？（v）TATS网络的复杂结构有多重要？（vi）电流不均匀性对管腔内离子浓度有什么影响？（vii）TATS是否对心力衰竭中观察到的功能变化有贡献？尽管在许多方面缺乏实验证据，但计算机模型提供了一种评估和预测TATS可能功能的方法；这些模型表明，尽管表面膜和TATS膜在电方面偶联良好，但TATS内离子通量途径的集中，加上受限扩散，可能导致TATS管腔内的离子组成与细胞外总体空间中的离子组成不同，并随活性和病理状况而变化。
