Histochemical study of glycoconjugates in the toadfish Halobatrachus didactylus oesophagus epithelium

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 Galβ1,3GalNAc, α/βGalNAc, Galβ1,4GlcNAc, αL-Fuc and internal βGlcNAc residues (PNA, SBA, RCA120, UEA I, LTA and KOH-sialidase-WGA affinity). Galβ1,4GlcNAc, αL-Fuc and internal βGlcNAc were also found in the glycocalyx. The sacciform cells expressed sialyloligosaccharides terminating with Neu5acα2,3Galβ1,4GlcNac, Neu5Acα2,6Gal/GalNAc, Neu5AcForssman pentasaccharide (MAL II, SNA, KOH-sialidase-DBA staining) as well as asialoglycoconjugates with terminal/internal αMan (Con A affinity) and with terminal Galβ1,3GalNAc, Forssman pentasaccharide, Galβ1,4GlcNAc, GalNAc (HPA and SBA reactivity), αGal (GSA I-B4 reactivity), D-GlcNAc (GSA II labelling), αL-Fuc. The basal cells cytoplasm exhibited terminal/internal αMan and terminal Neu5Acα2,6Gal/GalNAc, Galβ1,4GlcNAc, α/βGalNAc, αGal, GlcNAc, αL-Fuc. Intermediate cells showed oligosaccharides with terminal/internal αMan and/or terminating with Neu5Acα2,6Gal/GalNAc, Galβ1,4GlcNAc in the cytoplasm and with Neu5acα2,3Galβ1,4GlcNac, α/βGalNAc, αGal, GlcNAc, αL-Fuc in the glycocalyx. The pyramidal cells expressed terminal/internal αMan and terminal Neu5Acα2,6Gal/GalNAc, GalNAc, αGal, αL-Fuc in the entire cytoplasm, terminal Neu5acα2,3Galβ1,4GlcNac and Forssman pentasaccharide in the apical extension, internal βGlcNAc and/or terminal αL-Fuc in the luminal surface, Neu5acα2,3Galβ1,4GlcNac, Neu5Acα2,6Gal/GalNAc, Galβ1,4GlcNAc, αGal in the basolateral surface. The flattened cells displayed glycans with terminal/internal αMan and terminal Neu5Acα2,6Gal/GalNAc, α/βGalNAc, αGal, D-GlcNAc in the entire cytoplasm, glycans terminating with Galβ1,3GalNAc and/or internal βGlcNAc in the sub-nuclear cytoplasm.