Study On The Antioxidative Responses In Mice Exposed To Gaseous Elemental Mercury

Gaseous mercury as global pollutant, caused a national scientists and scholars of great concern.When Hg enters human body by inhalation, it is oxidized to Hg2+ in red blood cells and other tissues, where it binds to proteins and accumulates. Hg2+ ion can easily combine with the mercapto-group of some enzymes incells, such as cytochrome oxidase, pyruvate kinase, fumaric reductase, and causes their inactivation, resulting in cell metabolism disorder, even cell death.Therefore, investigations on the mechanisms of Hg poison as well as protective measures against theHg-induced damage to organisms are important theoretically and practically.In this study, 5 week-old healthy male albino mice weighing 25±2 g were randomly divided into five groups including control group, Hg-exposed group, salicylic acid (SA)+ Hg group, N-acetyl-L-cysteine (NAC)+ Hg group, and vitamin C (Vc)+ Hg group, with 5 animals each group. SA of 5.5 mg/kg body weight, NAC of 300 mg/kg. and Vc of 100 mg/kg were supplied every other day before 4 days of Hg exposure until the Hg exposure end. The control group and Hg-exposed group were served with saline water. For Hg exposure, the animals were fumed in a glass-chamber with a constant dose of 500μg/m3 or 1000μg/m3 of Hg produced by a sealed internal mercury source for 10 h per day for 15 d. After the end of Hg exposure, the animals were killed, and the liver and lung tissues were harvested and washed three times with ice-cold physiological saline, weighted, wrapped with aluminum foil and stored in liquid nitrogen to be used. Data were collected on activities of superoxide dismutase (SOD), peroxidase (POD) in liver and lung, the composition of SOD and POD isoenzymes detected by polyacrylamide gel electrophoresis (PAGE). To address Hg-induced oxidative damage and the protective role of SA, NAC or Vc, lipid peroxidative levels were determined and expressed as the production of malondialdehyde (MDA). Results showed that exposure to Hg increased MDA levels, decreased the activities of SOD and POD in liver and lung which were confirmed by their isoenzyme constitutive patterns and activities exhibited by PAGE. Applications of SA, NAC or Vc effectively reduced the Hg-induced elevation of MDA levels, and alleviated the Hg-caused inhabitation of SOD and POD activities.In conclusion, the results in this study showed that Hg exposure resulted in oxidative damage as indicated by a significant increase in lipid peroxidation, and a decrease in activities of SOD and POD in mouse lung and liver. Application of SA, NAC or Vc might protect the animals against the Hg poison, which might be associated with the maintenance of activities of antioxidative enzymes in cells.For special stating, in this study, the NAC- and Vc-treated groups were used as positive controls protecting animal against Hg exposure and the role of SA was compared to the positive controls to reveal possible mechanisms of SA in animal responses to Hg exposure. To our knowledge, this is the first report in this sort.