title: Adaptation to hyperoxia in the neonatal rat: kinetic parameters of the oxygen-mediated induction of lung superoxide dismutases, catalase and glutathione peroxidase.
abstract: The activities of the enzymes superoxide dismutase, catalase and glutathione peroxidase increase in the lungs of neonatal rats exposed to normobaric hyperoxia. The oxygen-mediated increase in activity of these enzymes, known from previous studies to be an inductive response, was studied in 10- and 25-day-old rats as a function of both oxygen concentration and length of time of exposure to greater than 95% oxygen. In the lungs of 10-day-old rats the increase in superoxide dismutase, catalase, and glutathione peroxidase occurs only at 80% ambient oxygen or greater. In 25-day-old rats a similar pattern of response occurs with pulmonary catalase and glutathione peroxidase. However, unlike the response in 10-day-old rats, pulmonary superoxide dismutase does not increase in oxygen-exposed 25-day-old rats. The time course of enzyme induction was different for 10-day-old rats compared with 25-day-old rats. Exposure of 10-day-old rats to 95+% oxygen resulted in a significant increase in activity of superoxide dismutase after only 4 h when compared with air-exposed control animals. Catalasee and glutathione peroxidase in the same age group increased significantly after 6 h and 12 h of exposure to oxygen, respectively. Maximal levels of superoxide dismutase, catalase and glutathione peroxidase were reached after 6, 12 and 24 h of exposure to hyperoxia, respectively. This level of activity was then maintained throughout the subsequent exposure time up to 96 h. The activity of pulmonary catalase and glutathione peroxidase in 25-day-old rats did not increase significantly after 6 h of exposure to hyperoxia. An apparent plateau of increased activity was reached after 24 h of exposure. As observed with the 3 enzymes in 10-day-old rats, maximal enzyme activities were maintained throughout the subsequent period of oxygen exposure up to 96 h.
mesh_terms: D000222:Adaptation, Physiological; D000375:Aging; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D002374:Catalase / Q000096:biosynthesis*; D004790:Enzyme Induction / Q000187:drug effects; D005979:Glutathione Peroxidase / Q000096:biosynthesis*; D008168:Lung / Q000201:enzymology*; D010100:Oxygen / Q000506:poisoning*; D010544:Peroxidases / Q000096:biosynthesis*; D051381:Rats; D013482:Superoxide Dismutase / Q000096:biosynthesis*
chemical_list: D010544:Peroxidases; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D010100:Oxygen