Oxidative stress in songbirds exposed to dietary methylmercury
- 423 Downloads
Long-term, sublethal methylmercury exposure can cause reproductive depression, immune suppression, endocrine disruption and other problems in birds. We used two biomarkers to detect oxidative stress in livers of zebra finches (Taeniopygia guttata) developmentally exposed to sublethal levels of dietary methylmercury (0.0, 0.3, 0.6, 1.2, or 2.4 μg/g wet weight in diet). Our findings indicate that young adult finches exposed to environmentally relevant concentrations of mercury in ovo and through their diets, exhibited oxidative stress in their livers. We measured the ratio of the antioxidant glutathione in its reduced form (GSH) versus its oxidized form (GSSG) and the activity of the superoxide dismutase (SOD) enzyme suite. Blood total mercury served as a proxy for liver mercury concentration, and was on average 8.4 times the dietary dose (e.g., birds consuming 0.6 μg/g had blood mercury levels of ~5 μg/g on a wet weight basis). Consistent with what is known from large, aquatic bird species, there was a significant, negative relationship between GSH/GSSG ratios and tissue mercury concentrations, which is indicative of oxidative stress. This relationship was driven by a significant increase in the oxidized glutathione in the livers of birds with higher blood mercury levels. SOD activity was also found to have a significant, negative relationship with blood mercury.
KeywordsGlutathione Liver Mercury Oxidative stress Songbird Superoxide dismutase
This study was funded by E. I. DuPont de Nemours and Company and completed with oversight from the South River Science Team, which is a collaboration of state and federal agencies, academic institutions and environmental interests. Additional funding was provided by the Howard Hughes Medical Institute Undergraduate Science Education Program grant and a Llanslo-Sherman award from the Department of Biology at the College of William and Mary to KAH.
Conflict of interest
The authors declare that they have no conflict of interest.
- Gutteridge JM (1995) Lipid peroxidation and antioxidants as biomarkers of tissue damage. Clin Chem 41:1819–1828Google Scholar
- Hoffman DJ, Eagles-Smith CA, Ackerman JT, Adelsbach TL, Preston KR (2011) Oxidative stress response of Forster's terns (Sterna forsteri) and caspian terns (Hydroprogne caspia) to mercury and selenium bioaccumulation in liver, kidney, and brain. Environ Toxicol Chem 30:920–929. doi: 10.1002/etc.459
- Kenow KP, Hoffman DJ, Hines RK, Meyer MW, Bickham JW et al (2008) Effects of methylmercury exposure on glutathione metabolism, oxidative stress, and chromosomal damage in captive-reared common loon (Gavia immer) chicks. Environ Pollut 156:732–738. doi: 10.1016/j.envpol.2008.06.009 CrossRefGoogle Scholar
- McCord JM, Fridovich I (1969) Superoxide dismutase an enzymic function for erythrocuprein (hemocuprein). J Biol Chem 244:6049–6055Google Scholar