EDN1 and Ureteral obstruction: Additionally, results have suggested that ET-1 may play a role in the progression of interstitial fibrosis after ureteral ligation.[32] It has also been shown that ET-1 levels are higher in the renal vein than in the arterial inflow in UUO, suggesting that ET-1 production is renal in origin, rather than systemic.[33] The blockade of the ET-1 receptors prevents renal dysfunction and attenuates the decrease in renal plasma flow and glomerular filtration rate in rats subjected to ureteral obstruction.[34]