Antioxidant Defense System in Tadpoles of the American Bullfrog (Lithobates catesbeianus) Exposed to Paraquat

Abstract

Abstract There is a great need for proactive approaches to avoid amphibian declines. We investigated the possibility that antioxidant stress markers might serve as a proactive measure of physiological stress in anuran tadpoles. Commercially purchased American Bullfrog tadpoles (Lithobates catesbeianus, Gosner stage 36–37) were subjected to 0- (control), 0.1-, 0.5-, 1.0-, and 2.0-mg/L paraquat for 24 h. Liver and muscle (tail clip) tissues were removed and analyzed for catalase, superoxide dismutase (SOD), general peroxidase, and glutathione reductase (GR) activities. In the controls, there was no significant difference in GR activity in tissues collected from the liver and the tail; however, peroxidase, SOD, and catalase activities ranged from two- to 20-fold higher in the liver than in the muscle tissue. Treatment with paraquat resulted in significant increases in SOD, general peroxidase, and GR activities in the liver tissue, whereas the high constitutively expressed catalase activity remained unchanged...