Endothelial cells produce several vasoactive chemical factors, among them prostacyclin (PGI2), which induce vasodilatation of blood vessels and inhibit smooth muscle cell proliferation and platelet aggregation. The peptide endothelin is also produced by the endothelium, and is a potent constrictor of blood vessels and promotes cell proliferation. In a normal healthy state, prostacyclin helps counter-balance the actions of endothelin. In certain disease conditions, however, production of prostacyclin by the endothelium is impaired, allowing the deleterious effects of excessive levels of endothelin to predominate.

Dysfunction of the prostacyclin system occurs in several cardiovascular disorders, including thrombosis, myocardial infarction, stroke, myocardial ischemia, atherosclerosis and pulmonary arterial hypertension (PAH). Restoration of prostacyclin function using prostacyclin analogs that activate IP receptors improves prognosis for patients with PAH.