Figure 5.

Representative HE-stained lung sections (A–D) and lung sections stained for von Willebrand Factor (vWF; E–H) in rat pups kept in RA (A,B,E,F) or 100% O₂ (C,D,G,H) until 10 days of age. Lung morphometry, including the quantifications of alveolar crests (I,J), mean linear intercept (K) and number of pulmonary vessels per tissue ratio (L) was determined on paraffin sections in Wistar rats on day 10 kept in RA (open bars) or 100% O₂ for 10 days (shaded bars). Pups were injected daily with 0.9% NaCl or BMP9 (2.5 μg kg⁻¹ twice daily for 10 days). Values are expressed as mean ± SEM. N = 8. Differences between groups were analyzed by one-way ANOVA, followed by Tukey's multiple comparisons test. ^**p < 0.01 and ^***p < 0.001 vs. RA controls. ^†p < 0.05 and ^††p < 0.01 vs. age-matched O₂-exposed controls. Three independent experiments were performed. a, alveolus.