Abstract
The local regulation of intracellular calcium has been widely known to play an important role in the normal excitation-contraction coupling in the cardiac myocytes. While Ca2+ sparks do not normally trigger regenerative SR Ca2+ release (i.e. Ca2+ waves), under calcium overload conditions calcium sparks can trigger spontaneous calcium waves. While experimental imaging using confocal microscopy with fluorescent dyes is the major technique used to study calcium dynamics inside a cardiac myocyte, the dynamics of SR calcium during calcium overload is poorly understood and controversial. In the study presented here, we present a new temporal-spatial model of calcium sparks to examine this issue. The resolution is sufficiently high (100nm) so that all critical local fluxes can be properly considered. The model also takes into account the different expression levels of the sodium-calcium exchanger (NCX) and SERCA pumps near the SR Ca2+ release sites. From that, we want to demonstrate different factors contributing to the characteristics of Ca2+ sparks. This work includes an examination of the extent of SR calcium elevation, and how much calcium must be released to support the triggering of a sustained propagating Ca2+ wave within the cell. The findings presented here will be compared to published work in other studies.
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