endothelins

(= ET-1, ET-2, ET-3)

Group of peptide hormones (all 21 residues) released by endothelial cells. All have two disulphide bridges that hold them in a conical spiral shape. They are the most potent vasoconstrictor hormones known. Structurally related to the snake venom sarafotoxins. Pre-pro-endothelin-1 (203 residues) is cleaved to the biologically inactive big endothelin-1 (92 residues) by endothelin converting enzyme which will further cleave big endothelin to form active endothelin-1. ET-1, the predominant form, is produced by endothelial cells, ET-2 and ET-3 by various tissues. In addition to their vasoconstrictive properties, endothelins have inotropic and mitogenic properties, influence salt and water balance, alter central and peripheral sympathetic activity and stimulate the renin-angiotensin-aldosterone system. Though ET-1 acting through endothelin receptor(A) is vasoconstrictive, it acts through ET(B) to induce the release of nitric oxide which is a vasodilator.