Mediates the transport of urea driven by a concentration gradient across the cell membrane of the renal inner medullary collecting duct which is critical to the urinary concentrating mechanism. Mediates the transport of urea driven by a concentration gradient across the cell membrane of the kidney inner medullary collecting duct which is critical to the urinary concentrating mechanism. urea(in) = urea(out) urea(in) = urea(out) Inhibited by phloretin. Interacts with SNAPIN which enhances its urea transport activity. Epressed in the inner medulla of the kidney (at protein level). Expressed in the kidney. Belongs to the urea transporter family.