Computer-aided measurement of cell shortening and calcium transients in adult cardiac myocytes

The contractile cycle of the cardiac myocyte is essentially controlled by t he 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 wit h ion channels and contractile proteins. In this report we describe a novel method featuring up to 480 frames/s for monitoring rapid changes in cellul ar calcium and cell length, in which every individual cycle allows effectiv e evaluation of major cell parameters. Computers aid in determination of ti me to peak (in ms), time to 50% decrease (ms), diastolic Ca2+ (relative flu orescence units, rfu), systolic Ca2+ (rfu), Ca2+ transients (rfu), Delta Ca 2+/Deltat rise (rfu/s), and Delta Ca2+/Deltat fall (rfu/s). Contractile par ameters are as follows: maximum cell length (mum), minimum cell length (mum ), absolute cell shortening (mum), peak DeltaL/Deltat shortening (mum/s), a nd peak DeltaL/Deltat relaxation (mum/s). In summary, we succeeded in demon strating that this system is a unique and valuable tool that allows simulta neous and accurate assessment of contractile parameters and of calcium move ments of isolated adult cardiac myocytes.