Water transport mediated by murine urea transporters: implications for urine concentration mechanisms.

Urea transporters (UTs) facilitate urea diffusion across cell membranes and play an important role in the urinary concentration mechanisms in the kidney. Herein, we injected cRNAs encoding for c-Myc-tagged murine UT-B, UT-A2 or UT-A3 (versus water-injected control) in oocytes and evaluated oocyte surface protein expression with biotinylation and immunoblotting, urea uptake using [C] counts and water permeability (P ) by video microscopy. Immunoblots of UT-injected oocyte membranes revealed bands with a molecular weight consistent with that of a UT monomer (34 kDa), and UT-injected oocytes displayed significantly increased and phloretin-sensitive urea uptake and P when compared to day-matched control oocytes.