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. 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. 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. 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) urea(in) = urea(out) urea(in) = urea(out) Inhibited by phloretin (PubMed:8958221). Activated by vasopressin, forskolin, 3-isobutyl-1-methylxanthine (IBMX) and cAMP (PubMed:16959825). Inhibited by phloretin. Inhibited by urea analogs and phloretin and activated by forskolin. Inhibited by phloretin and activated by forskolin. Interacts with SNAPIN which enhances its urea transport activity. Vasopressin increases expression in the cell membrane. Expressed in the inner medulla of the kidney. Expressed in the inner medulla of the kidney. Expressed in both the inner and outer renal medulla of the kidney. Expressed in both the inner and outer renal medulla of the kidney. Induced by dehydration. Belongs to the urea transporter family. It is uncertain whether Met-1 or Met-9 is the initiator.