Double-immunolabeling of CCD with aquaporin-2 (AQP2) and Rhcg in floxed Rhcg, B1-Cre positive mice. Double-immunolabel for AQP2 (blue) and Rhcg (brown) was performed to identify the Rhcg-negative cells in floxed Rhcg, B1-Cre-positive mice. Principal cells, identified by apical AQP2 immunolabel, expressed Rhcg immunolabel (arrowheads). Intercalated cells, identified as AQP2-negative cells, did not express detectable Rhcg immunolabel (arrows).