The actions of ET-1 are mediated by 2 G-protein–coupled receptors,ETA and ETB.ETA receptors are expressed on pulmonary smooth musclecells and mediate vasoconstriction and cellular proliferation.ETB receptors are expressed mainly on the endothelialsurface of vessels and mediate vasodilation by producing nitric oxide andprostacyclin; however, in hypertension and other cardiovascular diseases, they arealso upregulated in vascular smooth muscle cells, where they have the samepathophysiologic actions as ETA receptors [24]. The gene discussed is EDN1; the disease is hypertensive disorder.