Histochemical Demonstration of Two Subtypes of O-linked Oligosaccharides in the Rat Gastric Glands

The gastric glands synthesize glycoproteins whose oligosaccharides are linked to the peptide core mainly by the O‐glycosidic bond, specifically removed by β‐elimination procedure. Our aim was to research the possibility of the existence of two subtypes of O‐linked oligosaccharides with a different behavior to the removal procedure. The lectins from peanut (PNA) and Maackia amurensis (MAA‐I) were histochemically used as markers of the O‐linked oligosaccharides. Sections were also pretreated with β‐elimination and/or peptide N‐Glycosidase F (PNGase‐F) for the specific removal of O‐ and N‐linked oligosaccharides, respectively. The lectin GNA, which mainly labels to N‐linked oligosaccharides, was used to test the correct working of PNGase‐F. To test the possibility that the β‐elimination treatment could remove the terminal sialic acid residues, the lectin LFA was used. The surface epithelium was negative to PNA, while it became strongly positive when β‐elimination was performed for 1 day. This staining was resistant to PNGase‐F, suggesting that PNA was labeling to O‐linked oligosaccharides. However, after β‐elimination for 5 days this staining is not observed. A similar pattern appeared with MAA‐I. We propose the existence of two subtypes of O‐linked oligosaccharides: labile and resistant. The labile O‐linked oligosaccharides are removed with β‐elimination for 1 day, unmasking the PNA‐positive oligosaccharides. These oligosaccharides are resistant O‐linked oligosaccharides because staining is abolished with longer treatment of β‐elimination. The results with MAA‐I also support this suggestion. In summary, the labile O‐linked oligosaccharides are removed with short treatment, while the resistant O‐linked oligosaccharides need a stronger procedure (for 5 days). Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.