Imaging of calcium wave propagation in guinea-pig ventricular cell pairs by confocal laser scanning microscopy.

We describe here the use of a confocal laser scanning microscope for imaging fast dynamic changes of the intracellular calcium ion concentration (Ca2+]i) in isolated ventricular cell pairs. The scanning apparatus of our system, paired galvanometer mirrors, can perform narrow band scanning of an area of interest at a high temporal resolution of less than 70 msec per image. The actual Ca2+]i is obtained directly through the fluorescence intensity of injected fluo-3, which responds to changes of Ca2+]i in optically sectioned unit volumes of the cell. Images of the calcium wave obtained during propagation between paired cells revealed that the wavefront is constant in shape and propagates at constant velocity without any delay at the cell-to-cell junction. The confocal laser scanning microscope with depth-discriminating ability is a valuable tool for taking pictures of the sequence of biological events in living cells.