Abstract
Hyperoxia and its effects on lung phagocyte function were tested by exposing rabbits to a FiO2-0.95+ or 0.21 for 2, 4, and 7 days after birth. In vitro oxidative metabolism of lung phagocytes, obtained by lavage, was studied by polarographic measurement of O2 consumption±1mM cyanide. In vivo pulmonary clearance was ascertained by comparing the numbers of viable Staphylococcus aureus in the left lung at 0 and 6 hours after aerosol infection, and bacterial ingestion was measured by histologic examination of the right lung. Lavage effluents contained >94% alveolar macrophages (AM) through 4 days of exposure. After 7 days, the mean number of granulocytes in lavages of O2-exposed animals rose to 77% and the group's cumulative mortality increased to 20% vs 4% in control litters. The mean clearance of S. aureus by control was 63, 60, and 72% at 2, 4, and 7 days vs O2-exposed newborns which killed 64, 19 and 26% of the inhaled bacteria at those ages(p<0.02 O2 vs control at 4 days). Impaired killing was not due solely to decreased ingestion because the mean numbers of intracellular bacteria exceeded 60% at 6 hr after infection in every O2 and control group. At 4 days, O2-exposed AM had lower basal and stimulated mitochondrial O2 consumption (0.8±0.2 and 1.6±0.3 nmol O2 consumed/106AM/min, x±SEM, n = 6) vs control AM (1.7±0.2 and 2.9±0.3, n = 6, p<0.02). Hyperoxia alters phagocytic killing of inhaled S. aureus by neonatal AM and is associated with diminished mitochondrial O2 consumption. Granulocytes become a secondary lung defense after hyperoxia induces bactericidal dysfunction in the newborn AM.
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Sherman, M. 1835 HYPEROXIA AND PHAGOCYTIC FUNCTION IN NEONATAL LUNG. Pediatr Res 19, 416 (1985). https://doi.org/10.1203/00006450-198504000-01853
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DOI: https://doi.org/10.1203/00006450-198504000-01853