OXIDANT-ANTIOXIDANT BALANCE IN ALVEOLAR MACROPHAGES FROM NEWBORN RATS

An oxidant-antioxidant imbalance in neonatal alveolar macrophages (AMs ) may contribute to the increased susceptibility to lung injury descri bed in the neonatal period. We therefore evaluated oxygen radical prod uction by rat AMs at various postnatal ages, and measured in parallel cellular antioxidant enzyme activities. AMs were obtained by bronchoal veolar lavage from rats aged <24 h, 21 days and 5 weeks, and results w ere compared to those obtained with adult rat AMs. Intracellular produ ction of oxygen radical species, estimated fluorometrically using 2',5 '-dichlorofluorescein diacetate as the substrate, was significantly re duced in neonates as compared with adults, both in the presence and in the absence of cell stimulation with phorbol myristate acetate (PMA) or opsonized zymosan, A similar pattern was observed for the extracell ular release of oxygen radical species, evaluated by lucigenin-enhance d chemiluminescence (CL) or peroxidase-catalysed CL oxidation of lumin ol: peak CL values measured after cell stimulation with PMA or opsoniz ed zymosan remained significantly lower for AMs from newborn rats than for AMs from adults, By contrast, high values for antioxidant enzyme activities (superoxide dismutase and glutathione peroxidase) in AMs we re demonstrated in newborns as compared to adults. We conclude that hi gh antioxidant activity in rat AMs after birth may be at least partly responsible for the low production of oxygen metabolites observed duri ng the same period.