Calcium-sensing receptors: extracellular calcium homeostasis and beyond -Donald Ward and Daniela Riccardi (p.8)

Intracellular calcium is a ubiquitous second messenger that controls many aspects of cell function. Its concentration in the cytosolic compartment ([Ca2+ ]i) can change dramatically, rising after stimulation by Ca2+ – mobilizing agonists from a resting level of -100 nM to tens of micromolar – an increase of a hundredfold.