Fig. 5.

Representative lung sections stained for the macrophage marker CD68 (A–D) or myeloperoxidase (MPO) as a marker for neutrophilic granulocytes (E–H) of rat pups kept in room air (RA; A, B, E and F) or 100% O₂ (C, D, G and H). Pups were injected daily with arginine buffer (A, C, E and G) or ibuprofen (50 mg/kg/day; B, D, F and H) until 10 days of age. a = alveolus. The influx of monocytes and macrophages (I) and neutrophilic granulocytes (J) was determined by morphometry on lung sections. RA pups (open symbols) and O₂ pups (solid symbols) were injected daily with arginine buffer (circles) or ibuprofen (50 mg/kg/day; triangles) until 10 days of age. Values are expressed as mean ± SEM (N = 6–7). **p < 0.01 and ***p < 0.001 versus RA controls. ^&p < 0.05 and ^&&&p < 0.001 versus age-matched arginine buffer-treated O₂-exposed controls