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首页> 外文期刊>American Journal of Physiology >Ca(2+) spark sites in smooth muscle cells are numerous and differ in number of ryanodine receptors, large-conductance K(+) channels, and coupling ratio between them.
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Ca(2+) spark sites in smooth muscle cells are numerous and differ in number of ryanodine receptors, large-conductance K(+) channels, and coupling ratio between them.

机译：平滑肌细胞中的Ca（2+）火花位点很多，并且在ryanodine受体的数量，大电导的K（+）通道以及它们之间的耦合比上也不同。

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摘要

Ca(2+) sparks are highly localized Ca(2+) transients caused by Ca(2+) release from sarcoplasmic reticulum through ryanodine receptors (RyR). In smooth muscle, Ca(2+) sparks activate nearby large-conductance, Ca(2+)-sensitive K(+) (BK) channels to generate spontaneous transient outward currents (STOC). The properties of individual sites that give rise to Ca(2+) sparks have not been examined systematically. We have characterized individual sites in amphibian gastric smooth muscle cells with simultaneous high-speed imaging of Ca(2+) sparks using wide-field digital microscopy and patch-clamp recording of STOC in whole cell mode. We used a signal mass approach to measure the total Ca(2+) released at a site and to estimate the Ca(2+) current flowing through RyR [I(Ca(spark))]. The variance between spark sites was significantly greater than the intrasite variance for the following parameters: Ca(2+) signal mass, I(Ca(spark)), STOC amplitude, and 5-ms isochronic STOC amplitude. Sites that failed to generate STOC did so consistently, while those at the remaining sites generated STOC without failure, allowing the sites to be divided into STOC-generating and STOC-less sites. We also determined the average number of spark sites, which was 42/cell at a minimum and more likely on the order of at least 400/cell. We conclude that 1) spark sites differ in the number of RyR, BK channels, and coupling ratio of RyR-BK channels, and 2) there are numerous Ca(2+) spark-generating sites in smooth muscle cells. The implications of these findings for the organization of the spark microdomain are explored.
机译：Ca（2+）火花是高度局部化的Ca（2+）瞬变，由Ca（2+）从肌质网通过ryanodine受体（RyR）释放引起。在平滑肌中，Ca（2+）火花激活附近的大电导，Ca（2+）敏感的K（+）（BK）通道，以产生自发的瞬时外向电流（STOC）。没有系统地检查引起Ca（2+）火花的单个站点的属性。我们已经表征了两栖动物的胃平滑肌细胞中的单个站点，同时使用宽场数字显微镜和全细胞模式的STOC膜片钳记录同时高速成像的Ca（2+）火花。我们使用信号质量方法来测量在站点释放的总Ca（2+），并估计流过RyR的Ca（2+）电流[I（Ca（spark））]。对于以下参数，火花部位之间的方差明显大于部位内部方差：Ca（2+）信号质量，I（Ca（spark）），STOC振幅和5毫秒等时STOC振幅。未能生成STOC的站点始终如此，而其余站点上的站点却没有失败地生成STOC，因此可以将站点划分为STOC生成站点和无STOC站点。我们还确定了火花位的平均数量，该数量最少为42 / cell，更有可能至少为400 / cell。我们得出的结论是1）火花位点在RyR，BK通道的数量和RyR-BK通道的耦合比上有所不同，以及2）在平滑肌细胞中有许多Ca（2+）火花产生位点。探索了这些发现对火花微区组织的意义。

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