Abstract: In order to explore the toxic effects of tetrabrominated diphenyl ether on the antioxidant defense system of fish and thus its potential harm to fish health, the effects of 2,2′,4,4′tetrabromodiphenyl ether (BDE-47) on the antioxidant defense system of tilapia liver were studied using the semistatic water exposure method. There were three exposure concentrations of 5, 50 and 500 μg·L^-1, and different sampling times of 1, 3, 7, 15 and 30 d. The results showed that the activity of antioxidant enzymes or the content of antioxidant factors in the liver of tilapia significantly changed after exposure to BDE-47, indicating BDE-47 exposure could cause oxidative stress and oxidative damage. According to the response of antioxidant enzymes in livers of tilapia exposed to BDE-47, SOD, CAT, and GSH were relatively sensitive antioxidant parameters. There was no significant doseeffect or time-effect relationships between BDE-47 exposure concentration and the activities of SOD, CAT, GST, and GPX, or the contents of GSH and GSSG in liver of tilapia. In general, CAT and GSH showed a trend of increasing firstly and then decreasing later. GST and GPX showed a trend of increasing firstly, then decreasing later, and finally returning to normal level. GSSG showed an increasing trend. SOD increased firstly and then decreased at low BDE-47 concentration of 5 μg·L^-1, whereas it decreased firstly and then increased at high BDE-47 concentrations of 50 and 500 μg·L^-1.

Key words: 2,2′,4,4′-tetrabromodiphenyl ether, tilapia, liver, antioxidant enzyme, semi-static test.