1.A.28.1.5
Urea transporter 1 or UT-B1 (Solute carrier family 14 member 1; Urea transporter of the erythrocyte) (Bagnasco 2006).  A phenylphthalazine compound, PU1424, is a potent UT-B inhibitor, inhibiting human and mouse UT-B-mediated urea transport with IC50 values of 0.02 and 0.69 mumol/L, respectively, and exerted 100% UT-B inhibition at high concentrations (Ran et al. 2016). Another potent inhibitor is the thienopyridine, CB-20 (5-ethyl-2-methyl-3-amino-6-methylthieno[2,3-b]pyridine-2,5-dicarboxylate) (Li et al. 2019). UT-B catalyzes transmembrane water transport which can be ued as a reporter system (Schilling et al. 2016).  Knocking out both UT1 and UT2 increases urine output 3.5-fold and lowers urine osmolarity (Jiang et al. 2016). The double knockout also lowered blood pressure and promoted maturation of the male reproductive system. Thus, functional deficiency of all UTs causes a urea-selective urine-concentrating defect with few physiological abnormalities in extrarenal organs (Jiang et al. 2016). UT-B may be related to the occurrence of melanoma and play a role in tumor development (Liu et al. 2018).