Schematic diagram of the UT-A1 construct introduced to produce the UT-A1+/+/UT-A3−/− mice. The construct has the native UT-A1 promoter, spliced to mouse Urea Transporter (mUT-A1) exon 1, the rabbit beta-globin intron 1, mUT-A1 exon 2, followed by the open reading frame (ORF) for UT-A1 , and then the 3′ untranslated region (3′UT) for UT-A1.