Abstract
To understand the role of the superoxide (O 2 −) radical in chromate-related genotoxicity, we investigated whether Cr(VI) can catalyze the Haber-Weiss cycle in vitro: O 2 − + Cr(VI) → Cr(V) + O 2 Cr(V) + H 2O 2 → Cr(VI) + ·OH + OH −. ESR and spin trapping techniques were utilized to monitor the O 2 − (produced using xanthine/xanthine oxidase), ·OH, and Cr(V) species. Superoxide dismutase as well as catalase inhibited the ·OH radical radical formation, attesting to the direct involvement of O 2 − and H 2O 2 in the process. ESR measurements also provided direct evidence for the formation of Cr(V). Kinetic measurements were consistent with the role of Cr(V) and H 2O 2 as intermediates in ·OH formation. These results indicate that in cellular media, especially during chromate phagocytosis, the O 2 /t radical can become a significant source of ·OH radicals and hence a significant factor in the biochemical mechanism of cellular damage due to Cr(VI) exposure.
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