Metals and Oxidative Stress

CARDOSO NANCY; GALLEANO MONICA

Antioxidants On Line Journal

Antioxidants and Life Quality

Lugar: Buenos Aires; Año: 2005 p. 1 - 7

   Metals have been postulated as important elements involved in oxidative stress situations, as well as prooxidant as antioxidant agents. Prooxidant action of metals would include multiple mechanisms, while antioxidant activity would be essentially associated with antioxidant enzymes, except for Zinc, which has been proposed as an antioxidant per se.   Iron seems to play a key role in toxicity mediated by metals, acting as prooxidant (catalyzing reactive oxygen species production) and as antioxidant (being part of the catalase). Additionally, it has been postulated that several other metals exert their action through iron displacement. As a consequence, major efforts have been developed in order to understand iron behavior under physiological and pathological situations. To this purpose, low-temperature electron paramagnetic resonance (EPR) constitutes an useful tool to detect several iron complexes with minimal sample manipulation. Experimental iron overload in rats (200 mg of iron/kg as iron dextran, i.p., 6 h) showed increases in total iron content in liver (2.7-fold) and in desferrioxamine-chelatable iron (8.6-fold). This expansion in the ?labile? iron pool was consistent with the raise in the indicators of oxidative damage previously reported.   Excess dietary and/or pharmacological supplementation of metals which are essential should be avoided due to the possible doble-faced effect of this elements. Many questions are still unaswered (distribution of catalytically active metals, site specific reactions, etc) and new methodologies need to be developed in order to future research in this area.