Ultrastructural localization of concanavalin a receptors in normal and SV₄₀‐transformed hamster and rat cells

The distribution of receptor sites for concanavalin A at the surface of normal and SV 40 ‐transformed hamster cell cultures has been studied with the electron microscope after application of the Con A‐peroxidase method. Both normal and transformed cells show a strongly positive reaction. Although it has not been possible in single cases to distinguish with certainty between normal and transformed cells, the cell‐coat reaction of the majority of malignant hamster cultures shows a striking tendency to be more unevenly distributed than in normal controls. This remains true for cultures after relatively few or after many passages, and for lines derived from in vivo induced tumors or from in vitro transformed cultures. This observation confirms results obtained in this laboratory from hamster cells transformed by Polyoma virus or Adenovirus 12. However, in a few rat fibroblast cultures transformed by SV 40 virus, we have so far not seen any difference in the cell‐coat reaction between normal and transformed cells. The possible reasons for the more irregular distribution of the cell‐coat reaction product of transformed hamster cells compared to normal controls are discussed.