Endothelial cells produce several vasoactive chemical factors, among them endothelin and nitric oxide, which work in opposition. Nitric oxide dilates blood vessels, prevents platelet adhesion, and inhibits cell proliferation.
Endothelin, however, is a powerful blood vessel constrictor that also promotes cell proliferation. In a normal healthy state, the body maintains a balance between nitric oxide and endothelin. In contrast, in certain disease states endothelin is produced in excess. In addition to causing vasoconstriction, the narrowing of blood vessels, excessive endothelin can: