Fig. 1.

Serial sections from the same region of the inner medulla of a control patient. A: section stained with aquaporin 1 (AQP1) and Yasue. B: section stained with AQP1, kidney-specific chloride channel ClC-Ka, and Yasue. In the section stained only with APQ1 (A), positively stained loops are red; in the section stained with both APQ1 and ClC-Ka (B), positively stained descending thin loops are magenta and ClC-Ka-positive ascending thin loops are blue. Serial sections in A and B allow one to trace a single tubule between them. Small arrows mark the same AQP1-positive descending loops (1, 2, and 3) in A and B. Large arrowheads mark unstained ascending thin loops in A that are seen as ClC-Ka-positive ascending loop in B. No Yasue-positive deposits are noted in this control patient. C, medullary collecting ducts. Scale bars = 150 μm.