Distribution of membrane particles and gap junctions in normal and transformed 3T3 cells studied in situ, in suspension, and treated with concanavalin A

Freeze-fracture techniques were used to study the ultrastructural distribution of plasma membrane particles in cultures of normal Balb/c and Swiss 3T3 and simian virus 40- or murine sarcoma virus-transformed fibroblasts. No apparent differences were observed. Cultures fixed in situ show a seemingly random distribution of membrane particles both in normal or in transformed cells. Treatment of cell cultures in situ with concanavalin A does not result in an altered pattern of particle distribution. EDTA-induced suspension of normal or transformed cells does not result, per se, in modification of the type of membrane particle distribution seen in cells fixed in situ. However, upon further incubation, a proportion of normal or transformed cells in suspension show a varying degree of particle aggregation following a network pattern. Concanavalin A treatment of normal and transformed cells in suspension does not result in a specific change of the pattern of particle distribution. Because it has been established that treatment with concanavalin A of simian virus 40-transformed Balb/c 3T3 fibroblasts causes pronounced clustering of the concanavalin A receptors at the outer-surface, our results probably imply independence of membrane particles and concanavalin A receptors of these transformed cells.