KALTENBACH, J.C.; FASZEWSKI, E.E.; Mount Holyoke College; Wheelock College: Glycoconjugates in larval and adult skin of the bullfrog, Rana catesbeiana

In general, amphibian skin is composed of epidermis, glands (which release secretions onto the epidermal surface), and dermal connective tissue containing a ground substance layer (GSL). The question then arises, are specific glyconjugates present in these components and do they change as the skin is remodeled during metamorphosis? With this in mind, we used UEA 1 and other lectins as probes to demonstrate the presence, localization, and metamorphic changes in terminal sugar residues of glycoconjugates in dorsal and ventral skin of aquatic larvae and semi-aquatic adult bullfrogs. In larval skin (stages V-XVI), UEA 1 staining, specific for fucose, was present in basal epidermal cells (but not in apical or skein cells) and in serous glands and the GSL. Moreover, this lectin proved to be a good marker for demonstrating a second GSL within the dermis. During climax (stages XIX-XXI), basal epidermal cells produce adult stratified squamous epithelium with all cells staining positive for fucose (including flask cells). On the other hand, UEA 1 staining in serous glands became less intense, and the GSLs were more discontinuous and less prominent. Overall, the pattern of UEA 1 staining was similar in both dorsal and ventral skin of all stages. Moreover, staining with additional lectins indicated that each lectin has a specific staining pattern. In conclusion, we have demonstrated the presence, localization, and changes in fucose and other sugar residues in the main skin components of Rana catesbeiana. Such sugar residues may be important in regulation of skin functions, e.g. water balance, in both the aquatic larvae and semi-aquatic adult.