Local calcium release in mammalian skeletal muscle
Local calcium release in mammalian skeletal muscle
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DOI：
10.1111/j.1469-7793.1998.377be.x
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发表时间：
1998-10-15
影响因子：
5.5
通讯作者：
Ríos, E
中科院分区：
文献类型：
--
作者：
Shirokova, N;García, J;Ríos, E
1.用共聚焦显微镜记录与Ca 2+释放相关的Fluo-5荧光，该荧光来自大鼠或青蛙的快缩肌的机械分离的单根肌纤维，电压夹在两个凡士林间隙室中.干预引起的钙离子火花在青蛙骨骼肌（低电压去极化，应用咖啡因）在大鼠纤维图像与大量释放三分区域一致，但没有可分辨的离散事件。在成年大鼠纤维中从未观察到Ca 2+火花。相反，胚胎小鼠肌管中有大量标准形态的火花.去极化诱导的三重和周围区域之间的荧光梯度（这是成比例的Ca 2+释放通量）达到峰值约20毫秒，然后衰减到一个稳定的水平。青蛙纤维的电导率大于大鼠纤维。在青蛙中，峰值与稳定梯度的比值（R）具有陡峭的电压依赖性，在-50 mV（n = 7）时达到最大值4.8。在大鼠中，R具有2.3（n = 5）的基本电压非依赖性值。Ca ~（2+）诱导的Ca ~（2+）释放，导致多个释放通道的协同开放，被认为是青蛙骨骼肌Ca ~（2+）火花和释放高峰相的基础。一个弥漫性的“小事件”的释放，类似于在这些大鼠中观察到的，也存在于青蛙和被认为是直接激活的电压。目前的结果表明，在这些大鼠纤维中，CICR对由去极化触发的Ca 2+释放的贡献很小，并且缺乏一致的通道开放。
1. Fluo-5 fluorescence associated with Ca2+ release was recorded with confocal microscopy in single muscle fibres mechanically dissected from fast twitch muscle of rats or frogs, voltage clamped in a two Vaseline-gap chamber.2. Interventions that elicited Ca2+ sparks in frog skeletal muscle (low voltage depolarizations, application of caffeine) generated in rat fibres images consistent with substantial release from triadic regions, but devoid of resolvable discrete events. Ca2+ sparks were never observed in adult rat fibres. In contrast, sparks of standard morphology were abundant in myotubes from embryonic mice.3. Depolarization-induced gradients of fluorescence between triadic and surrounding regions (which are proportional to Ca2+ release flux) peaked at about 20 ms and then decayed to a steady level. Gradients were greater in frog fibres than in rat fibres. The ratio of peak over steady gradient (R) was steeply voltage dependent in frogs, reaching a maximum of 4.8 at -50 mV (n = 7). In rats, R had an essentially voltage-independent value of 2.3 (n = 5).4. Ca2+-induced Ca2+ release, resulting in concerted opening of several release channels, is thought to underlie Ca2+ sparks and the peak phase of release in frog skeletal muscle. A diffuse 'small event' release, similar to that observed in these rats, is also present in frogs and believed to be directly activated by voltage. The present results suggest that in these rat fibres there is little contribution by CICR to Ca2+ release triggered by depolarization, and a lack of concerted channel opening.