LECTINS AS MARKERS FOR PLASMA-MEMBRANE DIFFERENTIATION OF AMPHIBIAN KERATINOCYTES

Various colloidal gold- and horseradish peroxidase-conjugated lectins have been used for the structural and ultrastructural localization of carbohydrate moieties of glycoconjugates in frog epidermis. Griffonia simplicifolia I (GSI) and Glycine max (SBA) lectins bind to keratinocyte plasma membranes, and show an apparent binding gradient from the stratum spinosum to the replacement cell layer. The binding of lectins to Lowicryl K4M-embedded epidermis confirmed the specific rection on the plasma membrane. Gold particles were more concentrated in plasma membranes of upper strata than in those of inner cell layers, and quantification of gold-lectin complexes bound to plasma membranes demonstrated a gradient from base to apex in the epithelium, as was apparently observed by light microscopy. GSI inhibited K+-stimulated p-nitrophenyl phosphatase of frog epidermis microsomes, and this activity showed a gradient from inner to outer cell layers similar to that observed for GSI and SBA lectins. Our results suggest that GSI and SBA lectins can be useful as markers for amphibian keratinocyte differentiation.