Diffusion in the Transverse-Axial Tubule System of Cardiac Myocytes
Diffusion in the Transverse-Axial Tubule System of Cardiac Myocytes
复制标题
心肌细胞横轴管系统的扩散
DOI：
10.1016/j.bpj.2016.11.682
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发表时间：
2017
影响因子：
3.4
通讯作者：
Kong C
中科院分区：
文献类型：
--
作者：
Kong C
心室肌细胞的兴奋-收缩（EC）耦合严重依赖于横轴（t-）小管的结构，这是表面肌膜的内陷。许多电流已被证明优先位于t管膜，包括l型钙电流，Na- ca交换，河豚毒素敏感的Na和稳态K电流（Orchard, Pásek, and Brette, 2009）。实验。物理。94:509-519)。有人认为，t系统内的膜折叠可能会引入一个缓慢的扩散区，这可能会影响EC耦合周期中这些电流的离子平衡（Hong et al. 2014）。新医学。20:624-632。)为了研究t小管系统中的扩散，我们使用电子断层扫描技术，对兔和小鼠心室肌细胞的t小管结构进行了研究。细胞也被灌注到含有不同分子量溶质的溶液中，以检查它们对t系统的渗透。荧光漂白后恢复（FRAP）用于检测静止肌细胞t小管内的运输。我们发现，尽管这两个物种的t小管直径和复杂性存在显著差异，但在~ 70kDa以下的溶质穿透以及FRAP期间荧光恢复的时间过程中，差异相对较小。这些数据表明，t管结构的总体差异对t管内扩散速率没有显著影响。这项工作得到了BHF和MRC的支持
Excitation-contraction (EC) coupling in cardiac ventricular myocytes is critically dependent on the structure of transverse-axial (t-) tubules, which are invaginations of the surface sarcolemma. Many currents have been shown to be preferentially located at the t-tubular membrane, including the L-Type calcium current, Na-Ca exchange, tetrodotoxin-sensitive Na and steady-state K currents (Orchard, Pásek, and Brette. 2009. Exp. Physiol. 94: 509-519). It has been suggested that membrane folding within the t-system may introduce a slow diffusion zone, which may have implications for ion balance for these currents during the EC coupling cycle (Hong et al. 2014. Nat. Med. 20: 624-632.). To investigate diffusion in the t-tubule system, we examined t-tubule structure in rabbit and mouse ventricular myocytes as two common experimental models, using electron tomography. Cells were also superfused with solutions containing solutes of varying molecular weight to examine their penetration into the t-system. Fluorescence Recovery After Photobleaching (FRAP) was used to examine transport within the t-tubules of quiescent myocytes. We found that despite marked differences in t-tubule diameter and complexity in the two species, there were relatively small differences in solute penetration below∼ 70kDa, and in the time-course of fluorescence recovery during FRAP. These data suggest that gross differences in t-tubule structure do not have marked effects on the rate of diffusion within t-tubules. This work was supported by the BHF and MRC