Fig. 5. Immunohistochemical localization of the UT (stained brown) in the turtle kidney using the affinity-purified UT antibody. Using the anti-turtle UT and anti-Na⁺,K⁺-ATPase antibodies in adjacent mirror sections, immunoreactivity for UT and Na⁺,K⁺-ATPase was detected on the apical cell membrane of epithelia along the late distal tubule (A) and the distal nephron (B), respectively. In contrast, in adjacent mirror sections immunolabeling with the turtle UT and the H⁺-ATPase antibodies was observed in the apical membrane of some epithelial cells in the late distal tubules (C) and in the intercalated cells along the late distal tubules (D), respectively. In C and D, filled and open arrowheads show the UT and H⁺-ATPase immunopositive tubules, and H⁺-ATPase immunopositive cells along the distal tubules, respectively. In adjacent mirror sections, no UT immunoreactivity was detected in the collecting duct (E) where H⁺-ATPase was expressed (F). Abbreviations: G, glomerulus; ED, early distal tubule; LD, late distal tubule; P, proximal tubule. Scale bars for A–F, 50 µm.