Site-specific distribution of epithelial cell-surface carbohydrates in rat oral mucosa

Abstract

The binding of two fluorescein-labelled lectins to epithelial cell surfaces was examined microspectrofluorimetrically in rat oral mucosa. Griffonia simplicifolia (GS-I-B4), which is specific for α-D-galactosyl end groups, labelled only basal cells, while Ulex europaeus (UEA-I), which is specific for α-L-fucosyl groups, labelled only spinous cells. The degree of binding of the lectins was dependent on the lectin concentration and the lectin pH. Different sites were examined. The labelling of basal cells by GS-I-B4 was maximal on the lateral borders of the tongue, and the fluorescence diminished medially; in contrast, the UEA-I labelling of the corresponding spinous cells was of undiminished intensity in the mediolateral direction across the entire lingual epithelium. There was a gradual increase in the binding of GS-I-B4 and UEA-I towards the posterior aspect of the tongue. In the mid-palate, there was stronger staining both of basal cells by GS-I-B4 and of spinous cells by UEA-I in the gingivae as compared to the centre of the palate. In anteroposterior sections of the fore- and mid-palate, the fluorescence intensity of basal cells was inversely related to that of spinous cells, with maximal labelling of basal cells by GS-I-B4 and corresponding minimal binding of spinous cells by UEA-I being evident at the crests of the transverse rugae, and the opposite pattern of staining by both lectins being noted at the bases of the rugae. In sections of the soft palate and buccal mucosa, there was uniform labelling of basal cells by GS-I-B4 and of spinous cells by UEA-I. There were no significant differences in cell numbers at sites where there was low and high lectin binding. The findings indicate that, in the rat oral mucosa, there is a specific topographical distribution in the expression of α-D-galactosyl groups on epithelial basal-cell surfaces (as demonstrated by GS-I-B4) and α-L-fucose residues on spinous cells (as shown by UEA-I).