A comparative study of four cytochemical detection methods of concanavalin A binding sites on the cell membrane

Abstract

Four different electron cytochemical methods to detect concanavalin A (ConA) binding sites on the plasma membrane of mouse fibroblasts were compared in this study. The ConA binding sites were made visible either by adding ConA, followed by horseradish peroxidase (HRP) or hemocyanin (HC), or by marking the sites with complexes of ConA with ferritin (Fer) or with micro-peroxidase (MP). HC and Fer are directly visible in the electron microscope; HRP and MP are detected by their electron-dense reaction product with diaminobenzidin and H 2O 2. Differences in sensitivity of the ConA binding sites for the different markers were found and resulted in a tentative interpretation of the labelling reactions. All experiments suggested that normal and transformed murine fibroblasts both have plasma membranes in which the binding sites can move equally well and can be induced to form clusters. These results are discussed in relation with the hypothesis that differences in clustering of ConA sites between normal and transformed cells are responsible for differences in the agglutinability by ConA of these cells.