Heterogeneity of T-Tubules in Pig Hearts.
Heterogeneity of T-Tubules in Pig Hearts.
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DOI：
10.1371/journal.pone.0156862
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
James AF
中科院分区：
文献类型：
--
作者：
Gadeberg HC;Bond RC;Kong CH;Chanoit GP;Ascione R;Cannell MB;James AF
T-小管是肌膜的内陷，在哺乳动物心肌细胞的兴奋-收缩偶联中起关键作用。虽然一般认为t-小管在心房肌细胞中实际上是不存在的，但最近对大型哺乳动物心房细胞的研究表明，t-小管可能比以前想象的要多。然而，心肌细胞之间t-小管网络的异质性程度仍不清楚。本研究的目的是研究猪心房肌细胞的t-微管网络，并与心室肌组织进行比较。心脏组织获自年轻雌性长白猪（Landrace白色猪，45-75 kg，5-6月龄）。用含胶原酶的溶液通过动脉灌注分离心肌细胞。在加载fluo-4-AM的场刺激的分离细胞中检查Ca 2+瞬变。使用di-8-ANEPPS使分离的细胞的膜可视化。在用Alexa-Fluor 488缀合的WGA染色的固定冷冻组织切片中观察T-小管。通过应用阈值和计算的t-小管密度（TTD）获得二值图像。距离映射方法用于计算到最近的t-小管的半距离（HDTT）。Ca 2+瞬变的时空特性似乎与离体心房肌细胞中功能性T-小管的缺乏一致。然而，在冷冻切片中，可以在心房细胞的亚群中鉴定出t-小管。虽然所有心室肌细胞的TTD >3%（平均TTD = 6.94± 0.395%，n = 24），但只有5/22的心房细胞如此。平均心房TTD（2.35± 0.457%，n = 22）低于心室TTD（P<0.0001）。TTD与细胞宽度相关（r = 0.7756，n = 46，P<0.0001）。TTD ≤3%的心房细胞HDTT（2.29±0.16 μm，n = 17）显著高于心室细胞（1.33±0.05 μm，n = 24，P<0.0001）和TTD >3%的心房细胞（1.65±0.06 μm，n = 5，P<0.05）。这些数据表明，猪心肌细胞之间的t-小管网络的程度相当大的异质性，这与细胞大小。
T-tubules are invaginations of the sarcolemma that play a key role in excitation-contraction coupling in mammalian cardiac myocytes. Although t-tubules were generally considered to be effectively absent in atrial myocytes, recent studies on atrial cells from larger mammals suggest that t-tubules may be more numerous than previously supposed. However, the degree of heterogeneity between cardiomyocytes in the extent of the t-tubule network remains unclear. The aim of the present study was to investigate the t-tubule network of pig atrial myocytes in comparison with ventricular tissue. Cardiac tissue was obtained from young female Landrace White pigs (45–75 kg, 5–6 months old). Cardiomyocytes were isolated by arterial perfusion with a collagenase-containing solution. Ca2+ transients were examined in field-stimulated isolated cells loaded with fluo-4-AM. Membranes of isolated cells were visualized using di-8-ANEPPS. T-tubules were visualized in fixed-frozen tissue sections stained with Alexa-Fluor 488-conjugated WGA. Binary images were obtained by application of a threshold and t-tubule density (TTD) calculated. A distance mapping approach was used to calculate half-distance to nearest t-tubule (HDTT). The spatio-temporal properties of the Ca2+ transient appeared to be consistent with the absence of functional t-tubules in isolated atrial myocytes. However, t-tubules could be identified in a sub-population of atrial cells in frozen sections. While all ventricular myocytes had TTD >3% (mean TTD = 6.94±0.395%, n = 24), this was true of just 5/22 atrial cells. Mean atrial TTD (2.35±0.457%, n = 22) was lower than ventricular TTD (P<0.0001). TTD correlated with cell-width (r = 0.7756, n = 46, P<0.0001). HDTT was significantly greater in the atrial cells with TTD ≤3% (2.29±0.16 μm, n = 17) than in either ventricular cells (1.33±0.05 μm, n = 24, P<0.0001) or in atrial cells with TTD >3% (1.65±0.06 μm, n = 5, P<0.05). These data demonstrate considerable heterogeneity between pig cardiomyocytes in the extent of t-tubule network, which correlated with cell size.