NOS3 and pulmonary arterial hypertension: Many hypoxia-induced disorders, including endothelial dysfunction, pulmonary artery vasoconstriction, and pulmonary hypertension (PH) are highly associated with impairment of the endothelial nitric-oxide synthase (eNOS) pathway and NO production [5, 6], especially in individuals who are prone to high-altitude illness [7].