Localization of retinol-binding protein and prealbumin in the human kidney with an unlabeled enzyme immunohistochemical method.

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Abstract
An unlabeled peroxidase-antiperoxidase (PAP) method on paraformaldehyde fixed and paraffin-embedded tissue sections was used to demonstrate the localization of retinol-binding protein (RBP) and prealbumin (PA) in the human kidney. The high specificity of the method was obtained by using highly purified primary and bridge antibodies after removing cross-reactive and heterophile antibodies which markedly contributed to background staining. The proximal convoluted tubular cells in the renal cortex were stained without exception with the antibodies to RBP and PA. The DAB reaction products, which appeared granular, were localized at the apical portions of the tubular cells. The finding coincides with the biochemical studies that RBP and PA were absorbed and catabolized in the proximal tubular cells after filtration through the glomeruli. From these results, it should be concluded that the specificity of the present method will provide a beneficial tool for the elucidation of RBP metabolism in the peripheral tissues.