Metamorphic changes in localization of sugars in skin of the leopard frog, Rana pipiens

A lectin histochemical study was carried out to determine the distribution of specific sugars in glycoconjugates within an important osmoregulatory organ, amphibian skin. Paraffin sections were made of Rana pipiens skin from dorsal and ventral regions of aquatic larvae in representative developmental stages as well as from several body regions of semiaquatic adult frogs. Sections were incubated with horseradish peroxidase (HRP)-conjugated lectins, which bind to specific terminal sugar residues of glycoconjugates. Such sites were visualized by DAB-H2O2. The following HRP-lectins were used: UEA-1 for alpha-L-fucose, SBA for N-acetyl-D-galactosamine, WGA for N-acetyl-beta-D-glucosamine, PNA for beta-galactose, and Con A for alpha-mannose. We found that lectin binding patterns in larvae change during metamorphic climax as the skin undergoes extensive histological remodeling; this results in adult skin with staining patterns that are specific for each lectin and are similar in all body regions. Such findings in R. pipiens provide additional insight into the localization of molecules involved in osmoregulation in amphibian skin.