AQP2 and Ureteral obstruction: Administration of a selective COX-2 inhibitor prevents downregulation of aquaporin-2 (AQP2) in inner medullary collecting ducts, abolishes the increase in urinary excretion of the PGE2 and PGI2 metabolite 6-keto-PGF1α, and attenuates the polyuria observed typically during the first day after the release of bilateral ureteral obstruction induced for 24 hours [115,116].