CA RELEASE CHANNEL/RYANODINE RECEPTOR MODULATION BY CA IN SARCOPLASMIC RETICULUM

心脏的兴奋收缩(EC)偶联依赖于这一过程 肌浆网钙诱导钙释放(CICR) (Sr)，它通过钙释放通道发生，通常称为 兰尼定受体(RyR)。生理性CICR被认为是由 钙微区与RyR‘s AT的随机相互作用 T形小管和SR释放终端之间的二联体连接( 局部控制假说)。随机钙释放事件，称为 钙火花被认为是EC偶联的基本事件，但 它们的确切性质是有争议的。我们试图确定是否 钙火花产生于单个或多个RyR通过检查 肌浆网钙耗竭的影响，应减少偶联 在附近的RyR之间。在大鼠身上研究了自发的钙火花 应用共聚焦显微镜和荧光钙离子检测心肌细胞 FLOO-3号探测器。开发了一种用于计数和测量的计算机算法 客观上，钙会在LineScan图像中产生火花。Thapsigarin(25-150纳米) 咖啡因可释放的SR钙消耗高达%。在SR期间 尽管钙的火花减少了，但还是强烈地观察到了钙的消耗。 频率(控制的30%)和幅度(大于OTR等于60% 控制)。在校正由于降低的可检测性而产生的偏差之后 对于较小的火花，我们发现火花频率与SR无关 而波幅与载荷成正比。我们的结论是， 尽管火花幅度取决于SR填充状态，但 火花的产生不依赖于SR钙负荷，因此不依赖于 局部钙释放速率。这意味着火花是单通道的。 事件，或远高于本地阈值的集体事件 再生。

Excitation contraction (EC) coupling in the heart depends upon the process of calcium-induced calcium release (CICR) from the sarcoplasmic reticulum (SR), which occurs via calcium release channels commonly referred to as ryanodine receptors (RyR). It is believed physiological CICR is mediated by the stochastic interaction between calcium microdomains and RyR's at the dyad junction between the t-tubule and the SR release terminal (the local control hypothesis). Stochastic calcium release events, known as calcium sparks are believed to be elementary events of EC coupling, but their exact nature is controversial. We sought to determine whether calcium sparks arise from a single or multiple RyR's by examining the effect of SR calcium depletion, which should decrease the coupling between nearby RyR's. Spontaneous calcium sparks were studied in rat ventricular myocytes using confocal microscopy and the fluorescent calcium probe fluo-3. A computer algorithm was developed to count and measure objectively calcium sparks in linescan images. Thapsigargin (25-150 nM) depleted caffeine-releasable SR calcium by up to 64%. During SR depletion, calcium sparks were robustly observed albeit at reduced frequency (30% of control) and amplitude (greater than otr equal to 60% of control). After correction for bias due to the reduced detectability of smaller sparks, we found that the spark frequency was independent of SR load whereas the amplitude was proportional to load. We conclude that, although spark amplitude depends on SR filling status, the frequency of spark generation is independent of SR calcium load and therefore of the local calcium release rate. This implies that sparks are single channel events, or collective events that are well above threshold for local regeneration.