Mammalian urea transporters.

Urea transporters (UTs) encoded by the Slc14a1 (UT-B) and Slc14a2 (UT-A) genes mediate urea flux across cellular membranes. Considerable research has accrued detailing the function and distribution of members of both subfamilies. Much research effort has focused on the kidney, where UTs are highly expressed and function to promote urine concentration. Interestingly, UTs are also expressed in several other tissues that are historically not primarily associated with urea metabolism. In this review, I describe the phenotypes of UT knockout and transgenic mice and highlight the major advances made possible by use of these animal models. Where pertinent, I contrast these findings with known human phenotypes associated with UT mutations.