The immune complexes were captured by adding 50 μl Protein A or G agarose/sepharose beads (Santa Cruz Biotechnology), followed by overnight

incubation at 4 °C with gentle rocking. The immunoprecipitates were collected by centrifugation at 1000 × g for 5 min at 4 °C and washed for selleck 4 times in PBS, each time repeating the centrifugation step. After the final wash, the pellets were suspended in 40 μl of electrophoresis sample buffer and boiled for 2–3 min. Western blot analysis was performed using primary anti-NHERF-1 or anti-NaPi-2a antibody. For immunohistochemistry, 5-μm-thick paraffin sections of paraformaldehyde-fixed kidneys from untreated wild-type mice (for anti-αKlotho staining), or from wild-type mice injected with rFGF23 (n = 4) or vehicle (n = 3) (for anti-NHERF-1 and anti-phosphoserine staining) were prepared. Before immunofluorescence staining, dewaxed sections

were pretreated with blocking solution containing 5% normal goat serum in PBS with 0.1% bovine serum albumin and 0.3% Triton X-100 for ABT-199 clinical trial 60 min. All following steps were performed in PBS containing 0.3% Triton X-100 and 5% normal goat serum. Without rinsing, sections were incubated with polyclonal rabbit anti-αKlotho (Alpha Diagnostics, 1:1000), or anti-NHERF-1 (Abcam, 1:300) and mouse monoclonal anti-phosphoserine (Alpha Diagnostics, 1:1,000) antibodies at 4 °C overnight. After washing, sections were incubated for 1.5 h with goat anti-rabbit Alexa 548 (for αKlotho and for NHERF-1 detection) and goat anti-mouse Alexa 488 (for P-Ser detection) secondary

antibodies (both from Invitrogen, diluted 1:400). Controls were performed by omitting either one or both secondary antibodies. Racecadotril The slides were analyzed on a Zeiss LSM 510 Axioplan 2 confocal microscope equipped with a 63 × oil immersion lens (NA 1.3). By use of the multitrack function, individual fluorochromes were scanned with laser excitation at 488 and 543 nm separately with appropriate filter sets to avoid cross talk. Controls were scanned with identical laser excitation and filter settings. Pictures were processed using Adobe Photoshop (overlays). Some mouse kidney paraffin sections were stained with hematoxylin and eosin (H&E) by routine methods. Statistics were computed using SPSS for Windows 17.0. The data were analyzed by t-test for comparison of 2 groups, or analysis of variance (ANOVA) followed by Student–Newman–Keuls (SNK) multiple comparison test for comparison of more than 2 groups. P values of less than 0.05 were considered significant. The data are presented as the mean ± SD. To address the question whether FGF23 has a direct effect on the renal proximal tubule, we first measured mRNA expression of αKlotho in proximal renal tubules harvested from mice by laser capture microdissection (LCM), and compared the expression level to that found in distal tubules. As shown in Fig.