Oxygen-induced lung injury in the newborn piglet.

Oxygen-induced lung toxicity was studied in artificially fed newborn miniature piglets. Paired littermates of newborn piglets were exposed to either 96-98% oxygen or air for 2, 4, 7 or 10 days. Development of pulmonary edema, as monitored by both the lung wet weight to dry weight ratio and the lung wet weight to body weight ratio, was evident 4 days after the start of oxygen exposure. Examination of light and electron micrographs showed that pulmonary edema was located mainly in the perivascular and interstitial spaces. Endothelial and type I cells were normal in appearance throughout the oxygen exposure. After exposure to 10 days of oxygen, type II cells appeared to show a decrease in the size of lamellar bodies and an increase in the number and size of mitochondria. The activity of pulmonary antioxidant defenses, as measured by the activity of superoxide dismutase (SOD), glutathione peroxidase (GP) and glutathione reductase (GR), and the level of reduced glutathione (GSH), showed a progressive increase in activity with duration of oxygen exposure, culminating in a significantly higher SOD, GP and GSH level in 7-day oxygen-exposed piglets. It is concluded that the newborn piglet is less susceptible to oxygen-induced lung injury compared to adults of other species, and the increase in the lung complement of SOD, GR, GP and GSH may contribute to the apparent resistance to oxygen toxicity.