Presented at the Wildlife Mercury Conference, Fairfax, Virginia, USA, April 12–13, 1996.
Effects of mercury and selenium on glutathione metabolism and oxidative stress in mallard ducks†
Article first published online: 26 OCT 2009
Copyright © 1998 SETAC
Environmental Toxicology and Chemistry
Volume 17, Issue 2, pages 161–166, February 1998
How to Cite
Hoffman, D. J. and Heinz, G. H. (1998), Effects of mercury and selenium on glutathione metabolism and oxidative stress in mallard ducks. Environmental Toxicology and Chemistry, 17: 161–166. doi: 10.1002/etc.5620170204
- Issue published online: 26 OCT 2009
- Article first published online: 26 OCT 2009
- Manuscript Accepted: 18 AUG 1997
- Manuscript Received: 19 FEB 1997
- Oxidative stress
Earlier studies have reported on the toxicity and related oxidative stress of different forms of Se, including seleno- D,L-methionine, in mallards (Anas platyrhynchos). This study compares the effects of Se (seleno-D,L-methionine) and Hg (methylmercury chloride) separately and in combination. Mallard drakes received one of the following diets: untreated feed (controls), or feed containing 10 ppm Se, 10 ppm Hg, or 10 ppm Se in combination with 10 ppm Hg. After 10 weeks, blood, liver, and brain samples were collected for biochemical assays. The following clinical and biochemical alterations occurred in response to Hg exposure: hematocrit and hemoglobin concentrations decreased; activities of the enzymes glutathione (GSH) peroxidase (plasma and liver), glutathione-S-transferase (liver), and glucose-6-phosphate dehydrogenase (G-6-PDH) (liver and brain) decreased; hepatic oxidized glutathione (GSSG) concentration increased relative to reduced glutathione (GSH); and lipid peroxidation in the brain was detected by increased thiobarbituric reactive substances (TBARS). Effects of Se alone included increased hepatic GSSG reductase activity and brain TBARS concentration. Selenium in combination with Hg partially or totally alleviated effects of Hg on GSH peroxidase, G-6-PDH, and GSSG. These findings are compared in relation to field observations for diving ducks and other aquatic birds. It is concluded that since both Hg and excess Se can affect thiol status, measurement of associated enzymes in conjunction with thiol status may be a useful bioindicator to discriminate between Hg and Se effects. The ability of Se to restore the activities of G-6-PDH, GSH peroxidase, and glutathione status involved in antioxidative defense mechanisms may be crucial to biological protection from the toxic effects of methylmercury.