NOS3 and pulmonary arterial hypertension: Interestingly, in bovine pulmonary artery endothelial cells, human saphenous vein endothelial cells, and in vivo in lungs of patients with pulmonary hypertension or in the aortas and mesenteric arteries of mice exposed to chronic intermittent hypoxia, the effect of hypoxia on eNOS may differ depending on whether the endothelium is arterial or venous.