Effect of oxygen on lung superoxide dismutase activities in premature baboons with bronchopulmonary dysplasia

We investigated the effects of gestational age and oxygen exposure on super oxide dismutase (SOD) activities in distal fetal lung tissue in primate mod els of bronchopulmonary dysplasia. During the final third of fetal life, lu ng coppper-zinc SOD (Cu,ZnSOD) specific activity decreased, whereas lung ma nganese SOD (MnSOD) specific activity tended to increase. In the premature newborn (140 days, 78% of term gestation), lung total SOD and Cu,ZnSOD spec ific activities decreased after 6-10 days of ventilation with as needed [pr o re nada (PRN)] or 100% oxygen compared with fetal control animals. Neithe r Cu,ZnSOD mRNA nor protein expression changed after either oxygen exposure at this gestation (140 days) relative to fetal control animals. At this ag e (6-10 days), lung MnSOD specific activity did not change in oxygen-expose d relative to fetal control animals, even though lung expression of MnSOD m RNA and protein increased after PRN or 100% oxygen exposure. In the very pr emature 125-day newborn (69% of term), lung Cu,ZnSOD specific activity and protein decreased, whereas Cu,ZnSOD mRNA increased, after 6-10 days of vent ilation with PRN oxygen compared with fetal control animals. In fetal lung explants, hyperoxia also decreased expression of SOD activity acutely (16-h exposure, 125 and 140 days gestation). To conclude, expression of SOD acti vity in the premature primate lung did not increase in response to elevated oxygen tension, apparently due to effects occurring subsequent to the expr ession of these mRNAs.