In vivo reduction of chromium (VI) and its related free radical generation

Chromium (VI) compounds are widely recognized as human carcinogens. Extensive studiesin vitroand in model systems indicate that the reactive intermediate, Cr (V), generated by cellular reduction of Cr (VI), is likely the candidate for the ultimate carcinogenic form of chromium compounds. Here we review our current understanding of the in vivo reduction of Cr (VI) and its related free radical generation. Our results demonstrate that Cr (V) is indeed generated from the reduction of Cr (VI)in vivoand that Cr (V) thus formed can mediate the generation of free radicals. Cr (V) and its related free radicals are very likely to be involved in the mechanism of Cr (Vl)-induced toxicity and carcinogenesis. These studies also illustrate thatin vivoEPR spectroscopy and magnetic resonance imaging can be very useful and powerful tools for studying paramagnetic metal ions in chemical and biochemical reactions occurring in intact animals. (Mol Cell Biochem 222: 41-47, 2001)