Reactive oxygen species and DNA oxidation in fetal rat tissues

It is well recognized that reactive oxygen species (ROS) are formed during the reperfusion of ischemic tissues and ROS may be pathogenic in adult tissues. Although there is little information on the formation and toxicity of ROS during prenatal life, a strong association has been made between limb and possibly brain malformations and uteroplacental ischemia during fetal stages of gestation. It has been proposed that these malformations result from attack by ROS formed during the resumption of placental perfusion. Studies reported here examined formation of ROS in teratogenically sensitive limb and brain and insensitive heart before and during the period of teratogenic sensitivity. Also examined was the formation of ROS following hypoxia and reoxygenation in fetal culture and DNA hydroxylation in sensitive and insensitive fetal tissues during uteroplacental ischemia and reperfusion in vivo. Rates of formation of superoxide anion radical and hydrogen peroxide declined with increasing gestational age whereas those for hydroxyl radical increased. Hydrogen peroxide generation was greatest in insensitive heart whereas hydroxyl radical formation was significantly lower in brain than in limb or heart, which had comparable rates. Hydrogen peroxide generation, which declined significantly in fetuses, but not in membranes with gestation, failed to respond to reoxygenation in vitro. Finally, there were significant increases in DNA hydroxylation in fetal hearts and limbs, but not in brains during uteroplacental ischemia but no further significant change could be detected after reperfusion.