EXPRESSION OF COPPER-ZINC SUPEROXIDE-DISMUTASE AND GLUTATHIONE-PEROXIDASE IN ORGANS OF DEVELOPING MOUSE EMBRYOS, FETUSES, AND NEONATES

The rise in antioxidant enzyme activity in the lungs of late-gestation fetuses is thought to be caused by the preparation of the pulmonary a ntioxidant system for birth. However, recent data have shown that such a rise also occurs in the livers of late-gestation fetuses. Consequen tly, this surge cannot solely be ascribed to the preparation of the pu lmonary antioxidant system for birth. In this study we examine the exp ression of copper/zinc superoxide dismutase (Sod1) and glutathione per oxidase (Gpx1) in various organs of late-gestational mouse fetuses. Fu rthermore, we compare the expression of these genes in organs of fetus es, neonates, and adult mice. These studies were carried out to invest igate whether the change in mRNA levels for these two genes is related to a developmental change in oxidant stress. Our data demonstrate tha t an increase in both Sod1 and Gpx1 mRNA occurs in lungs and livers of late-gestational mouse fetuses. The brain demonstrates an increase in Sod1 expression at or around the time of birth, the kidney shows an e levation in Gpx1 mRNA levels, and the heart fails to demonstrate a sur ge in both Sod1 and Gpx1 mRNA levels. Our data show that the liver is the organ with the highest levels of Sod1 and Gpx1 mRNA in embryos and neonates (immediately after birth). In the adult, the liver has the h ighest levels of Sod1 mRNA and the spleen the highest level of Gpx1 mR NA. These data suggest that the levels of Sod1 and Gpx1 mRNA are unrel ated to oxygen consumption and to oxygen tension exposure of individua l organs and do not necessarily appear to occur in the lung solely in preparation for birth. The reasons for the increase in antioxidant enz yme(s) mRNA levels in late gestation are more complex and may involve other factors.