EDN1 and pulmonary arterial hypertension: It has a long-lasting vasoconstrictive effect and is involved in vascular remodeling, fibrosis, cell proliferation, and apoptosis.16,33 Since pulmonary vasoconstriction and pulmonary hypertension are associated with BPD development, ET-1 is likely to be involved and might have a role as an early marker of BPD development.