Examining a new role for zinc in regulating calcium release in cardiac muscle

It is well established that mammalian cells contain a small but measurable pool of free or labile zinc in the cytosol that is buffered in the high picomolar range. Recent attention has focussed on the fact that this pool of free zinc has signalling effects that can be evoked through extracellular stimuli posing the question as to whether zinc should be regarded as a second messenger. Our knowledge of the targets, the biological significance, and the molecular mechanisms of zinc signalling is limited but recent evidence suggests that zinc homeostasis may be intimately linked to intracellular calcium signalling. In this review we discuss the role of zinc as an intracellular signalling molecule with an emphasis on the potential role of zinc in shaping calcium-dynamics in cardiac muscle. We also consider the evidence that the cardiac ryanodine receptor is a potential zinc signalling target.