Figure 4.

VIP-receptor immunostaining. (a) Immunocytochemical staining of cultured PASMCs. VPAC-1 shows weak and VPAC-2 strong expression in normal controls. Both are enhanced in PPH patients (scale bar = 10 μm). (b) Immunohistochemical staining of pulmonary blood vessels in paraffin-embedded lung tissue. Normal controls show a regular vessel wall and a wide lumen (L). VPAC-1 staining shows a tendency toward a zonal distribution of the receptors in the media, while the signal for VPAC-2 is distributed more evenly throughout the whole media. In PPH the vessels show a narrowing of the lumen. Both receptors, particularly VPAC-2, are upregulated in PPH (scale bar = 20 μm).