Imaging of Calcium Transients During Excitation-Contraction Coupling in Skeletal Muscle Fibers
Action potential stimulation of skeletal muscle fibers activates the release of Ca2+ from the sarcoplasmic reticulum (SR), thus leading to a fast and transient change in myoplasmic calcium concentration ([Ca2+]i). Until very recently these calcium transients have been only recorded by means of space averaging photodetectors, such as photomultipliers and photodiodes, in combination with the use of several intracellular calcium indicators1–8. The high frequency response exhibited by this kind of photodevices is ideal to track the fast calcium transients, characteristic of the muscle cells; however, their physical construction make them inherently unable to provide information about the topological distribution of the release process. Given the structural complexity of the muscle cells, it is possible that the limited knowledge gained so far has omitted important features of this physiological process. In an attempt to surmount these limitations we have adapted video microscopy techniques to perform rapid Ca2+-imaging in this preparation9. This has been a difficult task because the muscle fiber is a thick specimen (100–150 µm in diameter) able to undergo very fast changes in shape and volume as a consequence of its electrical activation.
KeywordsSkeletal Muscle Fiber Calcium Transient Nile Blue Fluorescence Transient Single Muscle Fiber
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