Tissue-specific changes in the activities of antioxidant enzymes during the development of the chicken embryo

1. Tissue-specific profiles of the expression of the antioxidant enzymes su peroxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT ) and the concentrations of reduced glutathione (GSH) during the developmen t of the chick embryo were investigated. 2. The liver, brain, yolk sac membrane (YSM), kidney, lung, heart and skele tal muscles were collected at the following days of embryo development: 10, 11, 13, 15, 17, 19, 21 and 22 (day-old chicks). 3. The different tissues of the embryo displayed distinct development strat egies with regard to the acquisition of antioxidant capacity. In the liver the specific activity of SOD increased between days 10 and 11 of developmen t, then significantly decreased up to day 15 and remained at the same value during the rest of the developmental period. GSH-Px specific activity incr eased through the time of development. CAT had 2 peaks of specific activity at day 10 of the development and in day-old chicks. 4. The brain was characterised by comparatively high SOD-specific activity especially during the last days of incubation. The specific activities of G SH-Px and CAT were low throughout development. 5. In the YSM maximal GSH-Px and CAT-specific activities were found on day 15 of incubation. In the kidney and heart GSH-Px-specific activity increase d at hatching time. CAT-specific activity in the kidney increased just afte r hatching. 6. It is concluded that each tissue studied expressed a profile of antioxid ant defence mechanisms to deal with oxidative stress at hatching time.