Single channel and 45Ca2+ flux measurements of the cardiac sarcoplasmic reticulum calcium channel.
Single channel and 45Ca2+ flux measurements of the cardiac sarcoplasmic reticulum calcium channel.
复制标题
心脏肌浆网钙通道的单通道和 45Ca2 通量测量。
DOI：
10.1016/s0006-3495(86)83543-3
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发表时间：
1986
影响因子：
3.4
通讯作者：
Meissner,G
中科院分区：
文献类型：
--
作者：
Rousseau,E;Smith,JS;Henderson,JS;Meissner,G
纯化的犬心肌肌浆网囊泡被动负载45 CaCl 2，并根据快速淬灭方案测定Ca 2+释放活性。微摩尔Ca 2+和毫摩尔腺嘌呤核苷酸可激活囊泡亚群的Ca 2+释放，而毫摩尔Mg 2+和微摩尔钌红可抑制囊泡亚群的Ca 2+释放。在10 μ M游离Ca 2+存在下，45 Ca 2+释放的流出半衰期为20 ms。向10 μ M游离Ca 2+中加入5 mM ATP可使流出增加两倍（t1/2 = 10 ms）。一个高电导的钙传导通道被纳入平面脂质双层从纯化的心肌肌浆网馏分。该通道在53 mM反式Ca 2+中显示出75 +/- 3 pS的单位电导，并且对Ca 2+与Tris+的选择性比率为8.74。该通道依赖于顺式Ca 2+的活性，也被刺激的毫摩尔ATP。微摩尔浓度的钌红和毫摩尔浓度的Mg 2+是抑制性的，并降低了单通道记录的开放概率。这些研究表明，心肌肌浆网含有高电导的Ca 2+通道，其释放Ca 2+的速率与兴奋-收缩偶联显著相关。
Purified canine cardiac sarcoplasmic reticulum vesicles were passively loaded with 45CaCl2 and assayed for Ca2+ releasing activity according to a rapid quench protocol. Ca2+ release from a subpopulation of vesicles was found to be activated by micromolar Ca2+ and millimolar adenine nucleotides, and inhibited by millimolar Mg2+ and micromolar ruthenium red. 45Ca2+ release in the presence of 10 microM free Ca2+ gave a half-time for efflux of 20 ms. Addition of 5 mM ATP to 10 microM free Ca2+ increased efflux twofold (t1/2 = 10 ms). A high-conductance calcium-conducting channel was incorporated into planar lipid bilayers from the purified cardiac sarcoplasmic reticulum fractions. The channel displayed a unitary conductance of 75 +/- 3 pS in 53 mM trans Ca2+ and was selective for Ca2+ vs. Tris+ by a ratio of 8.74. The channel was dependent on cis Ca2+ for activity and was also stimulated by millimolar ATP. Micromolar ruthenium red and millimolar Mg2+ were inhibitory, and reduced open probability in single-channel recordings. These studies suggest that cardiac sarcoplasmic reticulum contains a high-conductance Ca2+ channel that releases Ca2+ with rates significant to excitation-contraction coupling.