Modelling the calcium-induced periodic and anisotropic contraction of cardiac myocytes

Introduction Since the pioneering work of Fabiato and Fabiato (1975), studies on myocardial function from analysis of single cardiac muscle cells have received an increased attention. Experiments conducted at the isolated cell level enable an analysis of cardiomyocyte response to mechanical stress, as well as a visualisation of fast cytosolic and nuclear calcium dynamics in contracting cardiac myocytes. It is known that mechanical stress induces an increase of intracellular calcium concentrations and different possible transduction mechanisms have been proposed (Ruwhof, 2001). In addition to these cell membrane phenomena, the mechanism of calcium-induced calcium release (CICR) seems also involved (Fabiato, 1983). In this work, we analyse rhythmic cardiomyocytes contractions starting from the CICR model of Goldbeter et al. (1990). In addition, we consider the effect of anisotropic calcium diffusion and propose a mechano-chemical coupling of Ca ^ cytosolic concentrations with anisotropic cell sarcomeres contraction. The simulated spatio-temporal cell contractions are validated by comparison with timelapse videomicroscopic sequences of spontaneously and periodically contracting isolated rat cardiac myocytes.