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Developmental profiles of antioxidant enzymes and trace metals in chick embryo
J X Wilson1, E M Lui, R F Del Maestro
1Department of Physiology, University of Western Ontario, London, Canada.
Insights
During chick embryo development, key antioxidant levels like glutathione and superoxide dismutase activity rise with oxygen consumption. These changes suggest oxygen and metabolism regulate fetal antioxidant systems.
Area of Science:
- Biochemistry
- Developmental Biology
- Physiology
Background:
- Chick embryos (Gallus gallus domesticus) exhibit a transient increase in oxygen consumption midway through incubation.
- This metabolic shift is linked to developmental processes and oxidative stress.
Purpose of the Study:
- To investigate the relationship between embryonic oxygen partial pressure (PO2), oxidative metabolism, and antioxidant systems in chick embryos.
- To determine if antioxidant enzyme concentrations and activities correlate with metabolic changes during development.
Main Methods:
- Measurement of oxygen consumption rates and PO2 in developing chick embryos.
- Quantification of glutathione (GSH), zinc (Zn), and iron (Fe) concentrations in liver and brain tissues.
- Assay of antioxidant enzyme activities, including superoxide dismutase (SOD) and catalase, in embryonic tissues.
- Assessment of extra-mitochondrial hydrogen peroxide release.
Main Results:
- Oxidative changes in chick embryos were paralleled by increased concentrations of glutathione and Zn in the liver, and elevated SOD activity in the brain.
- Antioxidant enzyme levels and cofactors were significantly higher in the liver compared to the brain.
- Hepatic catalase activity correlated with its cofactor, iron (Fe).
- Hydrogen peroxide release rates were substantially greater in embryonic liver than in brain.
Conclusions:
- Embryonic antioxidant systems, including glutathione and superoxide dismutase, appear to be regulated by oxygen partial pressure (PO2) and the rate of oxidative metabolism.
- Tissue-specific differences in antioxidant levels and cofactor abundance exist during chick embryonic development.
- This study provides initial insights into the dynamic regulation of fetal antioxidant defenses.
Abstract:
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 hydrogen 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.