TISSUE-SPECIFIC DIFFERENCES IN ANTIOXIDANT DISTRIBUTION AND SUSCEPTIBILITY TO LIPID-PEROXIDATION DURING DEVELOPMENT OF THE CHICK-EMBRYO

The purpose of this study was to determine the tissue-specific acquisi tion of antioxidant capacity during chick embryo development and to as sess the effectiveness of this process in the prevention of lipid pero xidation. The transfer of alpha-tocopherol, carotenoids and ascorbic a cid from the yolk/yolk sac membrane (YSM) to the developing chick embr yo and the distribution of these antioxidant compounds between the emb ryonic tissues were investigated. The concentrations of alpha-tocopher ol and carotenoids in the yolk decreased between day 15 of development and hatching at day 21, concomitant with an increase in the levels of these antioxidants in the YSM. The concentration of both these lipid- soluble antioxidants in the liver increased dramatically between day 1 8 of embryonic development and day 1 after hatching. The adipose tissu e content of alpha-tocopherol also increased markedly during the late embryonic/early neonatal period. However, the levels of alpha-tocopher ol in the liver were far higher than in any other tissue with particul arly low levels observed for the brain. Also, carotenoids were undetec table in the developing brain. Ascorbic acid was not present in the in itial yolk but high levels of this water-soluble antioxidant were dete cted in the YSM, particularly at the early stages of development. The concentration of ascorbic acid in the embryonic brain was far higher t han in any other tissue. Homogenates of brain tissue were extremely su sceptible to lipid peroxidation during incubation in vitro whereas ext racts of liver, yolk and YSM were relatively resistant to lipid peroxi dation, particularly in the absence of exogenous Fe2+.