Role of oxidative stress and antioxidant defense in 3,3 ',4,4 ',5-pentachlorobiphenyl-induced toxicity and species-differential sensitivity in chicken and duck embryos

The role of oxidative stress and antioxidant defense in 3,3',4,4',5-pentach lorobiphenyl (PCB 126)-induced toxicity and species-specific sensitivity wa s examined in White Leghorn chicken (Gallus domesticus) and Pekin duck (Ana s platyrhynchos) embryos. Eggs were injected into the air cell with 0.4-1.6 mug PCB 126/kg egg in corn oil prior to incubation, Lipid peroxidation mea sured by thiobarbituric acid reactive substances (TBARS), the GSSG:GSH rati o, and glutathione peroxidase (GPox) activities were determined in liver an d adipose tissue of day 19 chicken and day 26 duck embryos. In chicken embr yos, PCB 126 increased mortality and the incidence of edema and liver lesio ns, decreased embryo size, increased eye and head malformations, and marked ly reduced fat storage. In contrast, no effects on the endpoints were obser ved in duck embryos even at the highest dose used in chicken embryos. PCB 1 26 increased hepatic 7-ethoxyresorufin-O-deethylase (EROD) activity in a do se-dependent manner in chicken but not duck embryos. PCB 126 significantly increased TEARS levels in liver and to a greater degree in adipose tissue o f chicken embryos, indicating that adipose tissue is a sensitive target for this compound. Increases in lipid peroxidation by PCB 126 were associated with significant decreases in GPox activity in these tissues. These biochem ical changes support oxidative stress playing a role in PCB 126-induced emb ryo toxicity while antioxidant defenses provided protection against oxidati ve damage induced by this compound. Ducks, the less-sensitive species, show ed higher basal levels of hepatic GPox than chickens, suggesting that this antioxidant enzyme may contribute to the differences in sensitivity to this compound between the two species. (C) 2001 Academic Press.