EDN1 and stricture: ET-1 is the most potent and powerful endogenous vasoconstrictive peptide known today and it is 10 times more potent than angiotensin II.[29] ET-1 has been implicated in the tissue damage and dysfunction associated with UUO.[30] Kelleher et al.[31] demonstrated that ET-1 has a predominant role in the development of preglomerular arteriolar stenosis in the obstructed upper urinary tract.