Endothelin is any of a group of vasoconstrictive peptides, which are types of proteins produced by endothelial cells. It is secreted by the vascular endothelium from a 39 amino acid precursor, big ET-1, through the actions of an endothelin converting enzyme (ECE) found on the endothelial cell membrane. Endothelins constrict blood vessels and raise blood pressure. Three known endothelins, designated ET-1, ET-2, and ET-3, are chemically related to asp venom. ET-1 is the most potent vasoconstrictor yet discovered, being 10 times stronger than the second-most potent vasoconstrictor known, angiotensin II.
Receptors for endothelin are present in blood vessels and cells of the brain, choroid plexus and peripheral nerves. When applied directly to the brain of rats in picomolar quantities as an experimental model of stroke, endothelin-1 caused severe metabolic stimulation and seizures with substantial decreases in blood flow to the same brain regions, both effects mediated by calcium channels.