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

心脏中的兴奋收缩（EC）偶联取决于 肌浆网钙诱导钙释放（CICR） (SR)，其通过钙释放通道发生，通常称为 兰尼碱受体（RyR）。 据信生理性CICR是由 通过钙微区和RyR之间的随机相互作用， t-小管和SR释放末端之间的二分体连接（ 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 钙火花产生于一个或多个RyR的检查， SR钙耗竭的影响，这将减少偶联 在附近的RyR之间。本文研究了大鼠自发性钙火花 心室肌细胞共聚焦显微镜和荧光钙 荧光探针-3。一种计算机算法被开发出来用于计数和测量 在行扫描图像中客观地产生钙火花。毒胡萝卜素（25-150 nM） 消耗了高达64%的咖啡因释放SR钙。 SR期间 消耗，钙火花被强烈观察到，尽管在降低的 频率（对照的30%）和振幅（大于等于60%的OTR 控制）。 由于可检测性降低而校正偏倚后 对于较小的火花，我们发现火花频率与SR无关 载荷，而振幅与载荷成比例。 我们的结论是， 虽然火花振幅取决于SR填充状态，但 火花的产生与SR钙负荷无关，因此与 局部钙释放率。 这意味着火花是单通道的 事件，或集体事件，远高于当地的阈值 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.