Imaging Calcium Sparks in Cardiac Myocytes

Calcium ions play fundamental roles in many cellular processes in virtually all type of cells. The use of Ca²⁺ sensitive fluorescent indicators has proven to be an indispensable tool for studying the spatio-temporal dynamics of intracellular calcium ([Ca²⁺ ]_i ). With the aid of laser scanning confocal microscopy and new generation of Ca²⁺ indicators, highly localized, short-lived Ca²⁺ signals, namely Ca²⁺ sparks, were revealed as elementary Ca²⁺ release events during excitation–contraction coupling in cardiomyocytes. Since the discovery of Ca²⁺ sparks in 1993, the demonstration of dynamic Ca²⁺ micro-domains in living cardiomyocytes has revolutionized our understanding of Ca²⁺ -mediated signal transduction in normal and diseased hearts. In this chapter, we have described a commonly used method for recording local and global Ca²⁺ signals in cardiomyocytes using the fluorescent indicator fluo-4 acetoxymethyl (AM) and laser scanning confocal microscopy.