Paradoxical influence of Ca(2+) on lipid peroxidation.

Lipid peroxidation and Ca2+ are suggested to be linked as a mediator of cell damage and death. Lipid peroxidation is a free radical phenomenon. It is highly destructive process and induces plethora of alterations in structure and function of cellular membranes which could lead to cell injury. Ca2+, a regulator of variety of physiological and biochemical functions, was shown to enhance as well as inhibit lipid peroxidation. The explanations provided for the protection as well as the potentiation of lipid peroxidation by Ca2+ were, to some extent, speculative in nature and some of the basic facts seem to be overlooked. Moreover, Ca2+ has a closed-shell electronic state and lacks electronic transitions and hence it may not participate directly in a free radical reaction to modulate lipid peroxidation process. Perhaps this could be the reason for conflicting reports on this aspect. In the present review, the interactions between Ca2+ and lipid peroxidation are critically examined.