Evolution of calcium homeostasis: from birth of the first cell to an omnipresent signalling system.

Specific Ca(2+) homeostatic system appeared very early in the history of the cell, as a survival system preventing Ca(2+)-mediated cell damage. This homeostatic system produced a steep ( approximately 20,000 times) concentration gradient between extracellular and intracellular compartments, which has both survival importance (even relatively short increases in cytosolic Ca(2+) concentrations higher then 100 nM are incompatible with life) and signalling function. Evolution utilised this gradient together with an ability of Ca(2+) to interact with many biological molecules to create the most widespread and versatile signalling system, controlling the majority of cellular processes and executing complex routines of intercellular communications.