Ultrastructural distribution of lectin-binding sites in the glomerular wall of streptozotocin-induced diabetic rats.

Since carbohydrates-containing molecules are known to be preferentially altered in diabetes mellitus and that major functional and morphological alterations do occur during diabetes in the renal tissue, we revealed in the present study various lectin-binding sites in the glomerular wall of control and long-term diabetic animals. Lectin-binding sites specific to N-acetyl-galactosamine, N-acetyl-glucosamine, sialic acid, galactose and fucose were revealed using the appropriate lectin and the lectin-gold complex at the electron microscope level. Differences in intensity of labeling as well as in distribution were detected for several lectin-binding sites particularly in the glomerular basement membrane, reflecting the presence of additional glycoconjugates and changes in the molecular organization of the basement membrane components during diabetes. Alterations in the glycocomponents and the glycoproteins of the glomerular basement membrane as well as non-enzymatic glycosylation of the basement membrane components have been described in diabetes, going along with our present results. The alteration in the distribution of some lectin-binding sites gives support to modifications in the three dimensional organization of some glycoproteins which could occur in diabetes. Since the glomerular wall is actively involved in blood filtration, these changes may either induce, or result from, the loss in selective permeability and the massive proteinuria occurring during diabetes.