Fig. 3.

HO-1 overexpression and inhaled CO diminished the development of pulmonary vascular remodeling resulting from hyperoxia exposure. A: neonatal WT mice exposed for two wk to 75% O₂ develop right ventricular hypertrophy (RVH) that is significantly reduced in HO-1 TG and CO-treated mice (250 ppm, 1 h daily; n = 15–18 mice per group). B: vascular remodeling of pulmonary arterioles was also partially but significantly decreased in TG and CO-treated mice compared with WT mice following 2 wk of hyperoxic exposure (n = 4–6 mice per group). C: Representative paraffin sections from lungs stained with α-smooth muscle actin for the visualization of medial wall thickness of pulmonary arterioles (25- to 75-μm diameter) shows a decreased smooth muscle layer thickening in HO-1 TG and CO receiving mice compared with WT mice following exposure to 75% O₂. RV, right ventricle; LV, left ventricle; S, septum. **P < 0.01; ***P < 0.001 vs. WT-21% O₂; ##P < 0.01, ###P < 0.001 vs. WT-75% O₂. Scale bar in C = 30 μm.