Oxidative stress induced by chronic administration of sodium dichromate [Cr(VI)] to rats.

Chromium occurs in the workplace primarily in the valence forms Cr(III) and Cr(VI). Recent studies have demonstrated that sodium dichromate [Cr(VI)] induces greater oxidative stress as compared with Cr(III), as indicated by the production of reactive oxygen species by peritoneal macrophages and hepatic mitochondria and microsomes, and enhanced excretion of urinary lipid metabolites and hepatic DNA-single strand breaks (SSB) following acute oral administration of Cr(III) and Cr(VI). We have therefore examined the chronic effects of sodium dichromate dihydrate [Cr(VI); 10 mg (33.56 mumol)/kg/day] on hepatic mitochondrial and microsomal lipid peroxidation, enhanced excretion of urinary lipid metabolites including malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT), acetone (ACON) and propionaldehyde (PROP), and hepatic DNA damage over a period of 90 days. The maximal increases in hepatic lipid peroxidation and DNA damage were observed at approximately 45 days of treatment. Maximum increases in the urinary excretion of MDA, FA, ACT, ACON and PROP were 3.2-, 2.6-, 4.1-, 3.3- and 2.1-fold, respectively, while a 5.2-fold increase in DNA-SSB was observed. The results clearly indicate that chronic sodium dichromate administration induces oxidative stress resulting in tissue damaging effects which may contribute to the toxicity and carcinogenicity of hexavalent chromium.