Lipoperoxidation products and thiol antioxidants in chromium exposed workers

Hexavalent chromium is an established carcinogenic agent, which is not directly reactive with DNA. Its genotoxicity involves a reduction step, producing reactive oxygen species and radicals, and also lower valence forms which form stable complexes with intracellular macromolecules. The trivalent form of chromium may directly react with the genetic material and has also been shown to generate oxidative damage in vitro. To further evaluate the importance of in vivo oxidative DNA damage in the toxicity of each valence form, we conducted a comparative study on hexavalent and trivalent chromium-exposed workers (manual metal arc stainless steel welders and leather tanning workers), focusing on the total oxidative status by quantifying the level of lipoperoxidation products in urine. Thiol antioxidants are important in response to oxidative stress, and therefore, the concentration of glutathione and cysteine in peripheral blood lymphocytes was also determined. Chromium exposure was evaluated by quantifying total chromium in plasma and urine. Both groups had a significant increase in lipid peroxidation products expressed as malondialdehyde (MDA) in urine (tanners 1.42 +/- 0.61 micromol/g creatinine, welders 1.67 +/- 1.13 micromol/g creatinine versus controls 0.81 +/- 0.26 micromol/g creatinine, P < 0.005 in both cases) but only welders had a significant decrease in glutathione concentration in lymphocytes. There was a positive correlation between chromium in plasma and urinary MDA in welders, but not in tanners. This work is part of a larger study of which major results have been published previously including cytogenetics and DNA-protein cross-links in workers exposed to the two different forms of chromium. These results are compared with the results of oxidative damage from this study.