Fig. 1

Immunohistochemical staining of small pulmonary arteries in lung tissue sections. (Control = healthy Holstein heifers, HAPH = Holstein heifers with high altitude pulmonary hypertension. Means ± SEM (n = 6), *P < 0.05; **P < 0.01). (a) Verhoeff–Van Gieson staining (VVG) for elastin in small pulmonary arteries from healthy heifers. (b) Representative images of lung histological sections of heifers in HAPH group. Arrows indicate the proportional volume of elastin-positive adventitia. (c) Bar graphs representing the percentage area of vascular elastin in the small (diameter < 100 μm) and other (diameter ≥ 100 μm) pulmonary arteries. (d) Immunohistochemical staining of alpha smooth muscle actin (α-SMA) in small pulmonary arteries of Healthy heifer. (e) Representative images of histological lung sections from Holstein heifers with HAPH. Arrows indicate the proportional volume of the media layer. (f) Bar graph representing the percentage area of vascular media in small (diameter < 100 μm) and other (diameter ≥ 100 μm) pulmonary arteries. (g) Immunohistochemical staining of endothelial nitric oxide synthases (eNOS) in the healthy heifers. (h) Representative images of lung histological sections from heifers in the HAPH group. Arrows indicate immunostaining of eNOS. Scale bar = 50 μm. (i) Bar graph representing the relative immunostaining density of eNOS in pulmonary arterial endothelium (75 μm ≤ diameter < 100 μm). Scale bars = 100 μm