Cross-talk between reactive oxygen species and calcium in living cells.

The results of many investigations have shown that calcium is essential for production of reactive oxygen species (ROS). Elevation of intracellular calcium level is responsible for activation of ROS-generating enzymes and formation of free radicals by the mitochondria respiratory chain. On the other hand, an increase in intracellular calcium concentration may be stimulated by ROS. H2O2 has been recently shown to accelerate the overall channel opening process in voltage-dependent calcium channels in plant and animal cells. The 1,4,5-inositol-triphosphate-receptors as well as the ryanodine receptors of sarcoplasmic reticulum have also been demonstrated to be redox-regulated. Activity of Ca2+-ATPases and Na+/Ca2+ exchangers of animal cells are modulated by the intracellular redox state. Simultaneously, Ca2+ may activate antioxidant enzymes, such as plant catalase and glutathione reductase, and increase the level of superoxide dismutase in animal cells. Reviewed data support the speculation that Ca2+ and ROS are two cross-talking messengers in various cellular processes.