ENDOTHELIN, PEPTIDIC VASOCONSTRICTOR

Endothelin is a 21 aminoacids peptide belonging to the family of endothelium-derived contracting factors. It exists as 3 isoforms which have similar actions. It is principally, but not exclusively, synthesized and secreted by the vascular endothelial cells. Hypoxia, physical stretching and various endogenous substances stimulate its secretion. Its specific receptors are widespread in tissues, and the endothelin-receptor binding process produces a rise of intracellular calcium through the formation of inositol phosphate. Endothelin is the most potent of known vasoconstrictor substances. In addition, it acts on the myocardium and has a contracturant effect on other smooth muscle fibres. It also contributes to the release of endogenous peptides, inhibits platelet aggregation and has mitogenic properties. Endothelin can be determined in biological fluids, such as plasma, urine and cerebrospinal fluid, using immunoanalysis methods. Several pathological situations are associated with an increase of plasma endothelin concentrations ; these situations include arterial hypertension, myocardial infarction, cardiogenic shock and renal failure. Although not all physiopathological applications of endothelin have been elucidated, our current knowlegde of this substance indicates that it will be of importance in human medicine.