Wang S S, Thompson S H
Neurosciences Program, Stanford University, Pacific Grove, California 93950, USA.
Biophys J. 1995 Nov;69(5):1683-97. doi: 10.1016/S0006-3495(95)80086-X.
In many types of eukaryotic cells, the activation of surface receptors leads to the production of inositol 1,4,5-trisphosphate and calcium release from intracellular stores. Calcium release can occur in complex spatial patterns, including waves of release that traverse the cytoplasm. Fluorescence video microscopy was used to view calcium waves in single mouse neuroblastoma cells. The propagation of calcium waves was slowed by buffers that bind calcium quickly, such as BAPTA, but not by a buffer with slower on-rate, EGTA. This shows that a key feedback event in wave propagation is rapid diffusion of calcium occurring locally on a scale of < 1 micron. The length-speed product of wavefronts was used to determine that calcium acting in feedback diffuses at nearly the rate expected for free diffusion in aqueous solution. In cytoplasm, which contains immobile Ca2+ buffers, this rate of diffusion occurs only in the first 0.2 ms after release, within 0.4 micron of a Ca2+ release channel mouth. Calcium diffusion from an open channel to neighboring release sites is, therefore, a rate-determining regenerative step in calcium wave propagation. The theoretical limitations of the wave front analysis are discussed.
在许多类型的真核细胞中，表面受体的激活会导致肌醇1,4,5 - 三磷酸的产生以及细胞内钙库中钙的释放。钙释放可以以复杂的空间模式发生，包括穿越细胞质的释放波。荧光视频显微镜被用于观察单个小鼠神经母细胞瘤细胞中的钙波。钙波的传播被能快速结合钙的缓冲剂（如BAPTA）减慢，但不会被结合速率较慢的缓冲剂EGTA减慢。这表明波传播中的一个关键反馈事件是钙在小于1微米尺度上的局部快速扩散。波前的长度 - 速度乘积被用于确定在反馈中起作用的钙的扩散速率几乎与水溶液中自由扩散预期的速率相同。在含有固定Ca²⁺缓冲剂的细胞质中，这种扩散速率仅在释放后的最初0.2毫秒内发生，即在Ca²⁺释放通道口的0.4微米范围内。因此，从开放通道到相邻释放位点的钙扩散是钙波传播中一个决定速率的再生步骤。文中讨论了波前分析的理论局限性。
