Optical methods in calcium signaling

摘要

Calcium is an almost ubiquitous intracellular signal, controlling processes as diverse as fertilization and synaptic transmission, muscle contraction and metabolism. By its very nature, the Ca~2+ ion is an ephemeral signal. Increases in cytosolic Ca~2+ ([Ca~2+]_c) rapidly dissipate as a result of diffusion and the various pumps that help to maintain the remarkable Ca~2+ concentration gradient of about 10,000-fold between the cytosolic and extracellular compartments. Moreover, changes in [Ca~2+]_c cannot be preserved and measured in cell or tissue extracts. Thus, direct measurements of this most dynamic of intracellular signals must generally occur in intact living cell and tissue preparations. Measurements of [Ca~2+]_c must also provide temporal resolution consistent with the time-course of [Ca~2+]_c changes, which typically occur in milliseconds to seconds and may be localized to subcellular regions. By far the most successful approach to achieving these goals has been the introduction of Ca~2+-sensitive optical probes into cells, which can be monitored either globally, or with spatial resolution using appropriately equipped digital imaging microscopy systems