Mechanistic studies of relevance to the biological activities of chromium

Cellular uptake of Cr(VI), followed by its reduction to Cr(III) with the formation of reactive Cr(V/IV) intermediates, is a generally accepted cause of Cr(VI)-induced genotoxicity and carcinogenicity. Recently, Cr(III) oxidation to Cr(V) and/or Cr(VI) in biological systems came into consideration as a possible reason of anti-diabetic activities of some Cr(III) complexes, as well as of long-term toxicities of such complexes. The current review (with 142 references) summarizes the existing knowledge on the mechanisms of biologically relevant redox reactions of Cr(VI/V/IV/III) complexes. Applications of global kinetic analysis techniques, in conjunction with the methods for characterization of reactive intermediates (such as X-ray absorption spectroscopy, electrospray mass spectrometry, and EPR spectroscopy), for understanding the chemical basis of Cr biological activities, are illustrated with the examples from the authors' research. (C) 2004 Elsevier B.V. All rights reserved.