Digital Imaging System for Recording Rapid Changes in Intracellular Ca²⁺ Concentrations Triggered by Electrical Stimulation of Cardiac Myocytes

Abstract

To examine the origin and spreading of the Ca²⁺ transient following electrical stimulation of isolated myocyte, a system capable of recording intracellular Ca²⁺ distribution with sufficient temporal and spatial resolution was constructed. The system consists of a fluorescence microscope with computer-controlled pulse illumination and a digital image analyzer. The results with this new equipment show that the Ca²⁺ transient originates from one or a few points within a myocyte, and spreads throughout the cell. During the initial 60-msec period, the distribution of Ca²⁺ within a myocyte was not uniform. The system may be used for better understanding of the excitation-contraction coupling mechanism occurring within a cardiac myocyte or of changes in intracellular Ca²⁺ concentrations in other cells in which Ca²⁺ plays a crucial role in signal transduction.