Developmental profiles of antioxidant enzymes and trace metals in chick embryo

It has been previously well documented that partial pressure of oxygen (Po₂) and weight-specific rate of O₂ consumption in chick embryo (Gallus gallus domesticus) transiently increase midway through the 21-day in ovo incubation period. The present study found that these oxidative changes were paralleled by the concentrations of glutathione (GSH) and Zn in liver and by the specific activity of superoxide dismutase (SOD) in brain. Levels of antioxidant enzymes and their trace metal cofactors were markedly higher in liver than in brain. Hepatic catalase activity changed in parallel with the concentration of its cofactor, Fe. However, the relative abundance of metal cofactors did not appear to be the determining influence on other antioxidant enzyme activities. Rates of extra-mitochondrial hydorgen peroxide release were also much greater in liver than in brain. Taken together, the results of this initial study of embryonic chick antioxidant systems suggest that certain antioxidants may be regulated by Po₂ and rate of oxidative metabolism during fetal development.