Endothelin: an endothelium-derived vasoactive peptide.

Endothelin is a 21-amino-acid, vasoactive peptide. Sequence analysis of cloned cDNAs for porcine and human endothelin precursors showed that endothelin-1 (ET-1) is produced in the endothelial cells. The peptide, endothelin (ET), was first identified as a potent vasoconstrictor. It is one of the most potent endogenous vascular smooth-muscle constrictors, ten times more potent than angiotensin II, vasopressin, and neuropeptide Y. Shortly after the discovery of this vasoconstrictor peptide, it was revealed that endothelin also possesses vasodilator properties at doses lower than those necessary to produce vasoconstriction. However, controversy still exists over the mechanism(s) of action; prostacyclin and endothelium-derived relaxing factor (EDRF) have mainly been implicated as the source of the initial vasodepressor effect. ET also elicits markedly different regional hemodynamic response patterns. There is a heterogeneity in the observed vasodilation or vasoconstriction, depending on species and on vascular beds studied in the same species. Endothelin has been implicated in a number of pathologic situations, including tissue ischemia and vasospasm. ET seems to be produced more actively around the site of endothelial damage; the loss of balance between its vasodilator- and vasoconstrictor-induced responses could contribute to its patho-physiologic properties. Experimental results strongly support the concept that ET could be important in controlling vascular tonus, both in the healthy and the diseased vessel.