Cheng H, Lederer W J, Cannell M B
Department of Physiology, University of Maryland School of Medicine, Baltimore 21201.
Science. 1993 Oct 29;262(5134):740-4. doi: 10.1126/science.8235594.
Spontaneous local increases in the concentration of intracellular calcium, called "calcium sparks," were detected in quiescent rat heart cells with a laser scanning confocal microscope and the fluorescent calcium indicator fluo-3. Estimates of calcium flux associated with the sparks suggest that calcium sparks result from spontaneous openings of single sarcoplasmic reticulum (SR) calcium-release channels, a finding supported by ryanodine-dependent changes of spark kinetics. At resting intracellular calcium concentrations, these SR calcium-release channels had a low rate of opening (approximately 0.0001 per second). An increase in the calcium content of the SR, however, was associated with a fourfold increase in opening rate and resulted in some sparks triggering propagating waves of increased intracellular calcium concentration. The calcium spark is the consequence of elementary events underlying excitation-contraction coupling and provides an explanation for both spontaneous and triggered changes in the intracellular calcium concentration in the mammalian heart.
利用激光扫描共聚焦显微镜和荧光钙指示剂fluo-3，在静息的大鼠心肌细胞中检测到细胞内钙浓度的自发局部升高，即所谓的“钙火花”。与钙火花相关的钙通量估计表明，钙火花是单个肌浆网（SR）钙释放通道自发开放的结果，这一发现得到了钙火花动力学的雷诺丁依赖性变化的支持。在静息细胞内钙浓度下，这些SR钙释放通道的开放率较低（约每秒0.0001次）。然而，SR钙含量的增加与开放率增加四倍相关，并导致一些钙火花引发细胞内钙浓度升高的传播波。钙火花是兴奋-收缩偶联基础的基本事件的结果，并为哺乳动物心脏细胞内钙浓度的自发和触发变化提供了解释。
