Tsugorka A, Ríos E, Blatter L A
Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612, USA.
Science. 1995 Sep 22;269(5231):1723-6. doi: 10.1126/science.7569901.
In skeletal muscle cells, calcium release to trigger contraction occurs at triads, specialized junctions where sarcoplasmic reticulum channels are opened by voltage sensors in the transverse tubule. Scanning confocal microscopy was used in cells under voltage clamp to measure the concentration of intracellular calcium, [Ca2+]i, at individual triads and [Ca2+]i gradients that were proportional to calcium release. In cells stimulated with small depolarizations, the [Ca2+]i gradients broke down into elementary events, corresponding to single-channel currents of about 0.1 picoampere. Because these events were one-tenth to one-fifth the size of calcium sparks (elementary release events of cardiac muscle), skeletal muscle control mechanisms appear to be fundamentally different.
在骨骼肌细胞中，引发收缩的钙释放发生在三联体，即特化的连接部位，在此处肌浆网通道由横管中的电压传感器开启。在电压钳制下的细胞中使用扫描共聚焦显微镜来测量单个三联体处的细胞内钙浓度[Ca2+]i以及与钙释放成比例的[Ca2+]i梯度。在用小的去极化刺激的细胞中，[Ca2+]i梯度分解为基本事件，对应于约0.1皮安的单通道电流。由于这些事件的大小仅为钙火花（心肌的基本释放事件）的十分之一到五分之一，因此骨骼肌的控制机制似乎有根本的不同。
