Heterogeneous distribution of glycoconjugates in human kidney tubules

Abstract

Paraffin sections of normal human kidney were stained with a battery of ten lectin-horseradish peroxidase conjugates. Staining of proximal tubules revealed a relatively uniform distribution of glycoconjugates having bi- and/or triantennary N-linked sugar chains as well as terminal beta-galactose and alpha-fucose in all cells. In contrast, terminal alpha- and beta-galactose and alpha-fucose were localized in only some cells of the thin limbs, whereas N-linked sugar chains and terminal alpha-N-acetylgalactosamine occurred in all cells. In the ascending thick limbs, terminal alpha-N-acetylgalactosamine was found in some cells and N-linked sugar chains and terminal beta-galactose were present in all cells. The distal convoluted tubules contained N-linked oligosaccharides and terminal beta-galactose in all cells. Terminal alpha-N-acetylgalactosamine was found in some but not all profiles of distal convoluted tubules in a few kidneys. In the initial (connecting) segment of cortical collecting ducts, cells varied in their content of glycogen and glycoconjugates with terminal alpha- and beta-galactose, alpha-fucose and alpha-N-acetylgalactosamine, but cells in this segment evidenced uniform localization of N-linked sugar chains. A similar distribution of sugars occurred in the medullary ray segment of cortical collecting ducts, except for terminal beta-galactose which was present in all cells. In the medullary collecting ducts, there was also considerable cell-to-cell variation in the content and distribution of glycogen and glycoconjugates having N-linked sugar chains, terminal alpha-galactose, alpha-fucose, alpha-N-acetylgalactosamine, and the disaccharide galactose-(beta 1----3)-N-acetylgalactosamine. The content and distribution of glycoconjugates in the nephron varied only slightly between kidneys from different individuals, but individual variability was extensive in the collecting ducts. The reasons for these individual differences have not been determined, however. Cellular heterogeneity of glycosubstances within the different regions of the human kidney correlates with similar findings in other mammals and implies diverse functional roles for the various types of complex carbohydrates in the kidney.