It was further demonstrated that, in the lungs of patients with pulmonary hypertension, and an abnormal wall morphology in the endothelium of pulmonary arteries, eNOS expression was substantially reduced [14].We also found that the expression of eNOS was reduced in HAPH affected heifers, and this reduces the efficiency of plasma arginine utilization. Here, NOS3 is linked to pulmonary arterial hypertension.