Fig. 2. Localization of ephrin-B1, EphB2, EphB4 and EphB6 in the adult mouse kidney. Immunoperoxidase labeling of frozen sections with anti-ephrin-B1 (A), anti-EphB2 (B), anti-EphB4 (C) and anti-EphB6 (D) antibodies. (A) Ephrin-B1 immunoreactivity is broadly expressed in the nephron. In the proximal tubules (PT) of cortex, ephrin-B1 is localized in the basolateral membranes. Upper panel, anti-ephrin-B1p antibody; lower panels, anti-ephrin-B1e antibody. (B) EphB2 immunoreactivity is distinctly restricted to the medulla and absent from the cortex. EphB2 is localized in medullary tubules, including the distal straight tubules (DST) and the thin limb of the loop of Henle (TL). In the distal straight tubules, EphB2 is concentrated in the basal infolds. Upper panel, anti-EphB2p antibody; lower panel, anti-EphB2e antibody. (C) EphB4 is primarily localized in capillaries of the medulla (arrows in the lower panels). Faint immunoreaction of EphB4 is present in collecting duct (CD) in the cortex. (D) EphB6 immunoreactivity is primarily localized in tubules of the cortex and the outer medulla, including proximal tubules and distal tubules. In the distal straight tubules (DST) EphB6 is concentrated in the basal infolds and in the proximal tubules (PT) EphB6 is concentrated in granular structures of the cytoplasm. (E) There is no immunoreaction in the control without the primary antibodies. C, cortex; IM, inner medulla; OM, outer medulla; CD, collecting duct; DT, distal tubule; DST, distal straight tubule; PT, proximal tubule; TL, thin limb of the loop of Henle. Sections were developed with NiCl₂ (upper panel in A and B) or without NiCl₂ (lower panels in A and B, and all panels in C, D and E) and the sections in the lower panels except for the lower left of C were counterstained with hematoxylin. (F) Schematic drawings showing the expression patterns of ephrin-B1 (yellow), EphB2 (green), and EphB6 (blue) and predicted EphB2 tyrosine phosphorylation levels (dark green, high; light green, low) in the nephron. CD, collecting duct; CT, connecting tubule; DCT, distal convoluted tubule; DST, distal straight tubule (also known as thick ascending limb of loop of Henle); PCT, proximal convoluted tubule; PST, proximal straight tubule; TL, the thin limb of loop of Henle.