Properties of particle movement in the plasma membrane of 3T3 mouse fibroblasts

The effects of cytochalasin B, vinblastine and temperature on particle movement in the plasma membrane of several 3T3 mouse fibroblast lines were investigated. Preincubation of normal 3T3 cells for 24 h in 5-10 μg/ml cytochalasin B had no effect on the mean square relative displacement of marker particles in the membrane (motion constant), but preincubation for 4 h in 40 μg/ml vinblastine reduced the value of this constant by 70%. A 10 °C decrease in temperature decreased the motion constant in normal cells (Q₁₀ = 4) more than in virus-transformed 3T3 cells (Q₁₀ = 1.8). Interpreting the motion constant of the particles as an expression of the viscosity of the membrane material, values of 3 poise for normal 3T3 cells and 6 poise for the transformed cells are obtained for 37 °C and pH = 7.4. A method is suggested to quantitate aggregation of particles on the surface of cells. When this method is applied to gold particles on 3T3 cells, disaggregation of particles is seen to behave as an unordered process, whereas aggregation appears to express cellular control. This consideration and the effect of vinblastine indicate that the interpretation of particle movement as Brownian movement in a viscous membrane material does not cover all phenomena observed. The membrane movement of the flat revertant SVF1 101 [1] was investigated. This cell line occupies an intermediary position between normal 3T3 mouse fibroblasts and the polyoma and SV40 transformed 3T3 cell lines as judged by growth properties. Its membrane movement was found to occupy an intermediary position between the membrane movements of these cell lines, too.