[Lectin histochemistry of the Bufo marinus L. toad tongue]

Lectin histochemistry at light microscope level was used in the tongue of the cane toad Bufo marinus to determine the distribution of sugar residues in glycoconjugates (GCs) previously localized and characterized by conventional histochemical techniques. Five horseradish-peroxidase (HRP) labeled-lectins, namely Con A, PNA, SBA, UEA-1 and WGS were used. Additionally, neuraminidase (N) treated sections before the staining procedures were used in order to dilucidate the presence of terminal sialic acid (SA). Sugar residues in GCs of the taste organ (TO) associated mucous cells stained more intensely with WGA than with Con A and UEA-1. All the sensory cells reacted with Con A and WGA but one type of them were characteristically labeled by UEA-1. The glycocalix (gc) of the TOs resulted intensely stained with Con A and with WGA and UEA-1 before and after N treatment. The GCs in the mucous-supporting cells of dorsal mucosae filiform papillae and folds reacted intensely with WGA and weakly with Con A. The ciliated cells (cic) were intense and characteristically stained with UEA-1 and WGA and moderately with Con A. The gc reacted more intensely with WGA than with Con A. Dorsal mucosae glands secretory cells mucins were characteristically stained with PNA, SBA and WGA besides Con A, while glandular ciliated cells showed the same staining pattern as in the filiform papillae. In the ventral mucosa all epithelium cells resulted stained with WGA and Con A, while differentiated goblet cells only reacted as well with UEA-1 and PNA before and after neuraminidase treatment. Unexpectedly, ciliated ventral mucosae cells did not react with UEA-1 but only with WGA and Con A. The results have shown that lectin histochemistry is an interesting tool to characterize similarities and differences in the lingual GCs sugar residues composition and distribution, particularly those located in epithelial cells.