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Computer‐Aided Measurement of Cell Shortening and Calcium Transients in Adult Cardiac Myocytes

The contractile cycle of the cardiac myocyte is essentially controlled by the concentration of intracellular calcium ([Ca2+]i). Measurement of [Ca2+]i using Ca2+‐dependent fluorescence and simultaneous monitoring of cell dynamics enable characterization of a variety of substances interacting with ion channels and contractile proteins. In this report we describe a novel method featuring up to 480 frames/s for monitoring rapid changes in cellular calcium and cell length, in which every individual cycle allows effective evaluation of major cell parameters. Computers aid in determination of time to peak (in ms), time to 50% decrease (ms), diastolic Ca2+ (relative fluorescence units, rfu), systolic Ca2+ (rfu), Ca2+ transients (rfu), ΔCa2+/Δt rise (rfu/s), and ΔCa2+/Δt fall (rfu/s). Contractile parameters are as follows: maximum cell length (μm), minimum cell length (μm), absolute cell shortening (μm), peak ΔL/Δt shortening (μm/s), and peak ΔL/Δt relaxation (μm/s). In summary, we succeeded in demonstrating that this system is a unique and valuable tool that allows simultaneous and accurate assessment of contractile parameters and of calcium movements of isolated adult cardiac myocytes.