Endothelin 1 (ET-1), also known as preproendothelin-1 (PPET1), is a potent vasoconstrictorpeptide produced by vascular endothelial cells,[5] as well as by cells in the heart (affecting contractility) and kidney (affecting sodium handling).[6] The protein encoded by this gene – EDN1 – is proteolytically processed to release endothelin 1. Endothelin 1 is one of three isoforms of human endothelin.