Ultrastructural demonstration of the carbohydrate in developing rat enamel using soybean agglutinin-gold complexes

Fine structure and organic-inorganic relationships in early immature enamel, and the localization of N-acetyl-D-galactosamine in its matrix, were studied with a post-embedding demineralization and staining method, and a lectin-gold technique, respectively. Organic structures were observed that had similarities in shape but not in size to the original enamel crystals. Particles of colloidal gold coated with soybean agglutinin were scattered in the enamel region on the demineralized, unstained sections. After staining with uranyl acetate and lead citrate, gold particles were observed in close association with organic filamentous structures. These findings suggest that crystals of immature enamel are organic-inorganic structures, the organic structures of which contain N-acetyl-D-galactosamine.