Reduced Expression of Endothelial Nitric Oxide Synthase in the Lungs of Patients with Pulmonary Hypertension

TLDR: It is possible that decreased expression of nitric oxide synthase may contribute to pulmonary vasoconstriction and to the excessive growth of the tunica media observed in this disease.

Abstract: Background Pulmonary hypertension is characterized by abnormal thickening of the pulmonary arteries and increased pulmonary vascular resistance. Nitric oxide is a potent endothelium-derived vasorelaxant substance and an inhibitor of smooth-muscle-cell growth. Nitric oxide is produced in various cell types by the action of an enzyme, nitric oxide synthase. We compared the expression of endothelial nitric oxide synthase in the lungs of control subjects with that in the lungs of patients with pulmonary hypertension. Methods We investigated the expression of endothelial nitric oxide synthase by histochemical and immunohistochemical analysis, in situ hybridization, and Northern blot analysis in the lungs of 22 patients with plexogenic pulmonary arteriopathy (arteriopathy of grades 4 through 6), 24 patients with secondary pulmonary hypertension (arteriopathy of grades 1 through 3), and 23 control subjects. Results In the lungs of the control subjects, nitric oxide synthase was expressed at a high level in the v...