EDN1 and pulmonary arterial hypertension: Endothelin-1 is an endothelium-derived vasoconstrictor peptide that belongs to the endothelin/sarafotoxin family. The peptide works as a potent vasoconstrictor and its cognate receptors are therapeutic targets in the treatment of pulmonary arterial hypertension. It is involved in downstream GPCR-controlled signaling.