Microdomain [Ca2+] near ryanodine receptors as reported by L-type Ca2+and Na+/Ca2+exchange currents
Microdomain [Ca2+] near ryanodine receptors as reported by L-type Ca2+and Na+/Ca2+exchange currents
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DOI：
10.1113/jphysiol.2010.202663
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发表时间：
2011-05-15
影响因子：
5.5
通讯作者：
Sipido, Karin R.
中科院分区：
文献类型：
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作者：
Acsai, Karoly;Antoons, Gudrun;Sipido, Karin R.
L型钙通道（LTCCs）的钙内流触发肌浆网钙释放过程中，释放位点附近的[Ca 2 +]（nrs）暂时超过胞浆[Ca 2 +]。[Ca2+]（nrs）目前不能直接测量，但释放位点附近的Na+/Ca 2+交换剂（NCX）和LTCC也经历[Ca 2 +]（nrs）。我们已经测试了I-CaL和I-NCX可以校准以报告[Ca 2 +]（nrs）并报告不同的局部[Ca 2 +]时间过程和值的假设。在猪心室肌细胞中进行实验（全细胞电压钳，Fluo-3监测整体胞质[Ca 2 +]，37 ℃）。[Ca2+]（nrs）依赖性失活的I-CaL在一个步骤，以+10 mV的峰值约10 ms。对于I-NCX，我们计算分离的电流分数激活的[Ca 2 +]（nrs）;值最大在10 ms去极化。[Ca 2 +]（nrs）的回收率与两种报告基因相当（50 ms内> 90%）。校准产生的最大值[Ca 2 +]（nrs）之间的10和15 μ mol L-1与这两种方法。当施加到较低正电位（-30至-20 mV）时，[Ca 2 +]（nrs）的时程较慢，但峰值差异不大。总之，I-CaL失活和I-NCX激活，使用亚组分分析，可以用来报告[Ca 2 +]（nrs）的动态变化。通过这些不同方法获得的绝对值在相同范围内，表明它们报告了兰尼碱受体附近的类似功能区室。在+10 mV和-20 mV下的[Ca 2 +]（nrs）相当，表明尽管在这些电位下活化释放位点的数量不同，但释放位点的局部梯度可达到相似的值。
During Ca2+ release from the sarcoplasmic reticulum triggered by Ca2+ influx through L-type Ca2+ channels (LTCCs), [Ca2+] near release sites ([Ca2+](nrs)) temporarily exceeds global cytosolic [Ca2+]. [Ca2+](nrs) can at present not be measured directly but the Na+/Ca2+ exchanger (NCX) near release sites and LTCCs also experience [Ca2+](nrs). We have tested the hypothesis that I-CaL and I-NCX could be calibrated to report [Ca2+](nrs) and would report different time course and values for local [Ca2+]. Experiments were performed in pig ventricular myocytes (whole-cell voltage-clamp, Fluo-3 to monitor global cytosolic [Ca2+], 37 degrees C). [Ca2+](nrs)-dependent inactivation of I-CaL during a step to +10 mV peaked around 10 ms. For I-NCX we computationally isolated a current fraction activated by [Ca2+](nrs); values were maximal at 10 ms into depolarization. The recovery of [Ca2+](nrs) was comparable with both reporters (> 90% within 50 ms). Calibration yielded maximal values for [Ca2+](nrs) between 10 and 15 mu mol l-1 with both methods. When applied to a step to less positive potentials (-30 to -20 mV), the time course of [Ca2+](nrs) was slower but peak values were not very different. In conclusion, both I-CaL inactivation and I-NCX activation, using a subcomponent analysis, can be used to report dynamic changes of [Ca2+](nrs). Absolute values obtained by these different methods are within the same range, suggesting that they are reporting on a similar functional compartment near ryanodine receptors. Comparable [Ca2+](nrs) at +10 mV and -20 mV suggests that, although the number of activated release sites differs at these potentials, local gradients at release sites can reach similar values.