Altered distribution of ICa impairs Ca release at the t-tubules of ventricular myocytes from failing hearts.
Altered distribution of ICa impairs Ca release at the t-tubules of ventricular myocytes from failing hearts.
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DOI：
10.1016/j.yjmcc.2015.06.012
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发表时间：
2015-09
影响因子：
5
通讯作者：
Orchard CH
中科院分区：
文献类型：
--
作者：
Bryant SM;Kong CH;Watson J;Cannell MB;James AF;Orchard CH
在哺乳动物心室肌细胞中，钙的内流和释放主要发生在t小管，确保整个细胞内钙的同步释放。心衰与t小管结构破坏有关，但其对t小管功能的影响尚不清楚。因此，我们研究了冠状动脉结扎（CAL）或相应的假手术后18周大鼠心脏分离心室肌细胞t小管钙的内流和释放。用全细胞电压钳技术记录完整和去管化心肌细胞的l型Ca电流；使用电压和钙敏感荧光团的共聚焦显微镜监测t小管中的Ca释放。CAL与心脏和细胞肥大、射血分数降低、t小管结构破坏和更小、更慢的钙瞬态有关，但没有改变ryanodine受体分布、l型钙通道表达或ICa密度。在Sham肌细胞中，ICa主要位于t小管，而在CAL肌细胞中，ICa均匀分布在t小管和表面膜之间。用H-89抑制蛋白激酶A可引起CAL中t管ICa比Sham肌细胞更大的下降；在H-89存在的情况下，CAL的t管ICa密度小于Sham肌细胞。CAL肌细胞中较小的t管ICa伴随着t小管SR Ca释放的潜伏期增加和异质性，这可以通过使用硝苯地平减少ICa来模拟。这些数据表明，CAL通过不依赖于pka的机制降低t小管ICa，从而损害t小管Ca的释放，并导致心力衰竭中观察到的兴奋-收缩耦合改变。衰竭心肌细胞的全细胞钙电流（ICa）密度未发生改变。心肌细胞t小管中的ICa密度降低。t小管钙离子的减少与t小管钙离子释放受损有关。这些钙释放的变化可以通过使用硝苯地平降低钙离子来模拟。
In mammalian cardiac ventricular myocytes, Ca influx and release occur predominantly at t-tubules, ensuring synchronous Ca release throughout the cell. Heart failure is associated with disrupted t-tubule structure, but its effect on t-tubule function is less clear. We therefore investigated Ca influx and release at the t-tubules of ventricular myocytes isolated from rat hearts ~ 18 weeks after coronary artery ligation (CAL) or corresponding Sham operation. L-type Ca current (ICa) was recorded using the whole-cell voltage-clamp technique in intact and detubulated myocytes; Ca release at t-tubules was monitored using confocal microscopy with voltage- and Ca-sensitive fluorophores. CAL was associated with cardiac and cellular hypertrophy, decreased ejection fraction, disruption of t-tubule structure and a smaller, slower Ca transient, but no change in ryanodine receptor distribution, L-type Ca channel expression, or ICa density. In Sham myocytes, ICa was located predominantly at the t-tubules, while in CAL myocytes, it was uniformly distributed between the t-tubule and surface membranes. Inhibition of protein kinase A with H-89 caused a greater decrease of t-tubular ICa in CAL than in Sham myocytes; in the presence of H-89, t-tubular ICa density was smaller in CAL than in Sham myocytes. The smaller t-tubular ICa in CAL myocytes was accompanied by increased latency and heterogeneity of SR Ca release at t-tubules, which could be mimicked by decreasing ICa using nifedipine. These data show that CAL decreases t-tubular ICa via a PKA-independent mechanism, thereby impairing Ca release at t-tubules and contributing to the altered excitation–contraction coupling observed in heart failure. Whole-cell Ca current (ICa) density is not altered in myocytes from failing hearts. ICa density decreases in the t-tubules of myocytes from failing hearts. The decrease of t-tubular ICa is associated with impaired Ca release at t-tubules. These changes in Ca release can be mimicked by decreasing ICa using nifedipine.