The precarious antioxidant defenses of the preterm infant.

Oxygen radicals are considered to be major causative factors in many illnesses of preterm infants. This article reviews the antioxidant defenses in immature animals and preterm infants, and attempts to quantitate their vulnerabilities to oxidants. Sources of oxidants, including hyperoxia, iron, parenteral nutrition, nitric oxide, and prooxidants, and their impact on immature antioxidant defenses are discussed. Genetic manipulations of antioxidant enzymes such as knockout and transgenic mice models are reviewed. The various clinical and investigational antioxidant therapies in animals and humans and difficulties in the design of antioxidant therapy studies are explored.