Histochemical study of glycoconjugates in the toadfish Halobatrachus didactylus oesophagus epithelium

Abstract

The carbohydrate expression in the epithelium lining the oesophagus of the toadfish Halobatrachus didactylus was studied by means of conventional and lectin histochemistry. The stratified epithelium was constituted by basal cells, polymorphous cells in the intermediate layer, pyramidal and flattened cells in the outer layer and contained two types of large secretory cells: goblet cells and sacciform cells. PAS, Alcian blue pH 2.5 and pH 1.0 stained very strongly the goblet cells, weakly the surface of the other epithelial cells but did not stain the sacciform cells. The goblet cells cytoplasm contained oligosaccharides with terminal Galß1,3GalNAc, a/ßGalNAc, Galß1,4GlcNAc, aL-Fuc and internal ßGlcNAc residues (PNA, SBA, RCA120, UEA I, LTA and KOH-sialidase-WGA affinity). Galß1,4GlcNAc, aL-Fuc and internal ßGlcNAc were also found in the glycocalyx. The sacciform cells expressed sialyloligosaccharides terminating with Neu5Aca2,3Galß1,4GlcNac, Neu5Acß2,6Gal/GalNAc, Neu5AcForssman pentasaccharide (MAL II, SNA, KOH-sialidase-DBA staining) as well as asialoglycoconjugates with terminal/internal aMan (Con A affinity) and with terminal Galß1,3GalNAc, Forssman pentasaccharide, Galß1,4GlcNAc, GalNAc (HPA and SBA reactivity), aGal (GSA I-B4 reactivity), D-GlcNAc (GSA II labelling), aL-Fuc. The basal cells cytoplasm exhibited terminal/internal aMan and terminal Neu5Aca2,6Gal/GalNAc, Galß1,4GlcNAc, a/ßGalNAc, aGal, GlcNAc, aL-Fuc. Intermediate cells showed oligosaccharides with terminal/internal aMan and/or terminating with Neu5Aca2,6Gal/GalNAc, Galß1,4GlcNAc in the cytoplasm and with Neu5Aca2,3Galß1,4GlcNac, a/ßGalNAc, aGal, GlcNAc, aL-Fuc in the glycocalyx. The pyramidal cells expressed terminal/internal aMan and terminal Neu5Aca2,6Gal/GalNAc, a/ßGalß1,4NAc, aGal, aLFuc in the entire cytoplasm, terminal Neu5Aca2,3 Galß1,4GlcNac and Forssman pentasaccharide in the apical extension, internal ßGlcNAc and/or terminal aLFuc in the luminal surface, Neu5aca2,3Galß1,4GlcNac, Neu5Aca2,6Gal/GalNAc, Galß1,4GlcNAc, aGal in the basolateral surface. The flattened cells displayed glycans with terminal/internal aMan and terminal Neu5Aca2,6Gal/GalNAc, a/ßGalNAc, aGal, DGlcNAc in the entire cytoplasm, glycans terminating with Galß1,3GalNAc and/or internal ßGlcNAc in the sub-nuclear cytoplasm.