Endothelin 1

Endothelin 1 (ET-1), also known as preproendothelin-1 (PPET1), is a potent vasoconstrictor that in humans is encoded by the "EDN1" gene and produced by vascular endothelial cells. The protein encoded by this gene is proteolytically processed to release a secreted peptide termed endothelin 1. Endothelin 1 is one of three isoforms of human endothelin.
Source.
Preproendothelin is precursor of the peptide ET-1. Endothelial cells convert preproendothelin to proendothelin and subsequently to mature endothelin, which the cells release.
Clinical significance.
Long term ET-1 exposure has been associated with hypertrophic cardiomyopathy.
Endothelin-1 receptor antagonists (Bosentan) are used in the treatment of pulmonary hypertension. Inhibition of these receptors prevents pulmonary vasculature constriction and thus decreases pulmonary vascular resistance.