EDN1 and pulmonary arterial hypertension: Importantly, the findings that i.v. iron treatment reduced ET-1 in the lungs of fpnC326Yfl/fl SMMHC-CreERT2+ mice, and in the serum of acutely hypoxic individuals, and that in vitro iron treatment decreased ET-1 in PASMCs from PAH patients, provide a mechanism to underpin the benefits of iron supplementation reported in human studies.