Flask cells and flask-shaped glandular cells of amphibian skin specifically produce fucose-rich glycoproteins.

A battery of horseradish peroxidase-conjugated lectins has been employed as a cytochemical tool for the labelling of specific cell types in amphibian epidermis. Among the lectins used, only Ulex europaeus I (UEA I) showed specific reaction with the cytoplasm of flask cells. In addition, UEA I stained flask-shaped secretory cells in dermal glands and a reaction on glandular ductal cells was also observed. At the electron microscopic level, lectin binding was found in granules distributed among mitochondria in the cytoplasm of flask cells and in larger mucous granules of flask-shaped glandular cells, which were released into the lumen. UEA I also stained the extracellular space above flask cells. The labelling was due mainly to a glycoprotein of mol. wt. approx. 27 kDa. Structural and cytochemical similarities between flask cells and flask-shaped cells of dermal glands could be a consequence of a common secretory role of both cell types.