Department of Molecular Biophysics & Physiology, Rush University, Chicago, Illinois, USA.
Biophys J. 2010 May 19;98(10):2111-20. doi: 10.1016/j.bpj.2010.01.042.
Diastolic Ca leak from the sarcoplasmic reticulum (SR) of ventricular myocytes reduces the SR Ca content, stabilizing the activity of the SR Ca release channel ryanodine receptor for the next beat. SR Ca leak has been visualized globally using whole-cell fluorescence, or locally using confocal microscopy, but never both ways. When using confocal microscopy, leak is imaged as "Ca sparks," which are fluorescent objects generated by the local reaction-diffusion of released Ca and cytosolic indicator. Here, we used confocal microscopy and simultaneously measured the global ryanodine-receptor-mediated leak rate (J(leak)) and Ca sparks in intact mouse ventricular myocytes. We found that spark frequency and J(leak) are correlated, as expected if both are manifestations of a common phenomenon. However, we also found that sparks explain approximately half of J(leak). Our strategy unmasks the presence of a subresolution (i.e., nonspark) release of potential physiological relevance.
心肌细胞肌浆网（SR）的舒张 Ca 渗漏会降低 SR Ca 含量，为下一次搏动稳定 SR Ca 释放通道ryanodine 受体的活性。已经使用全细胞荧光全局可视化 SR Ca 渗漏，或使用共聚焦显微镜局部可视化，但从未同时使用这两种方法。当使用共聚焦显微镜时，渗漏被成像为“Ca 火花”，这是由释放的 Ca 和胞质指示剂的局部反应扩散产生的荧光物体。在这里，我们使用共聚焦显微镜同时测量完整的小鼠心室肌细胞中的全局ryanodine 受体介导的渗漏率（J(leak)）和 Ca 火花。我们发现火花频率和 J(leak)相关，这与如果两者都是共同现象的表现是一致的。然而，我们还发现火花仅解释了 J(leak)的大约一半。我们的策略揭示了潜在的亚分辨率（即非火花）释放的存在，这可能具有潜在的生理相关性。
