Various animal models of pulmonary hypertension have shown that an increase in both the cellular expression and circulating level of ET-1 could be found in chronic hypoxia (3 weeks of 10% O2), SU5416-hypoxia, and monocrotaline (MCT) models of PH, among others [124,125,126]. Here, EDN1 is linked to pulmonary arterial hypertension.