Williams D A, Fogarty K E, Tsien R Y, Fay F S
Nature. 1985;318(6046):558-61. doi: 10.1038/318558a0.
Calcium is believed to control a variety of cellular processes, often with a high degree of spatial and temporal precision. For a cell to use Ca2+ in this manner, mechanisms must exist for controlling the ion in a localized fashion. We have now gained insight into such mechanisms from studies which measured Ca2+ in single living cells with high resolution using a digital imaging microscope and the highly fluorescent Ca2+-sensitive dye, Fura-2. Levels of Ca2+ in the cytoplasm, nucleus and sarcoplasmic reticulum (SR) are clearly different. Free [Ca2+] in the nucleus and SR was greater than in the cytoplasm and these gradients were abolished by Ca2+ ionophores. When external Ca2+ was raised above normal in the absence of ionophores, free cytoplasmic Ca2+ increased but nuclear Ca2+ did not. Thus, nuclear [Ca2+] appears to be regulated independently of cytoplasmic [Ca2+] by gating mechanisms in the nuclear envelope. The observed regulation of intranuclear Ca2+ in these contractile cells may thus be seen as a way to prevent fluctuation in Ca2+-linked nuclear processes during the rise in cytoplasmic [Ca2+] which triggers contraction. The approach described here offers the opportunity of following changes in Ca2+ in cellular compartments in response to a wide range of stimuli, allowing new insights into the role of local changes in Ca2+ in the regulation of cell function.
钙被认为能控制多种细胞过程，通常具有高度的空间和时间精确性。为了使细胞以这种方式利用Ca2+，必须存在以局部方式控制该离子的机制。我们现在通过使用数字成像显微镜和高荧光Ca2+敏感染料Fura-2在单个活细胞中高分辨率测量Ca2+的研究，对这些机制有了深入了解。细胞质、细胞核和肌浆网（SR）中的Ca2+水平明显不同。细胞核和SR中的游离[Ca2+]高于细胞质，并且这些梯度被Ca2+离子载体消除。当在没有离子载体的情况下将外部Ca2+提高到正常水平以上时，游离细胞质Ca2+增加，但细胞核Ca2+没有增加。因此，细胞核[Ca2+]似乎通过核膜中的门控机制独立于细胞质[Ca2+]进行调节。因此，在这些收缩细胞中观察到的核内Ca2+调节可被视为一种防止在触发收缩的细胞质[Ca2+]升高期间Ca2+相关核过程波动的方式。这里描述的方法提供了跟踪细胞区室中Ca2+响应各种刺激而变化的机会，从而使人们对Ca2+局部变化在细胞功能调节中的作用有了新的认识。
