The role of negative charge in spontaneous aggregation of transformed and untransformed cell lines.

No correlation between net negative surface charge as determined by electrophoretic light-scattering techniques and the rates of spontaneous aggregation of 3T3MIT and SVPy 3T3MIT cells has been found. Neuraminidase treatment of both 3T3MIT cells and SVPy 3T3MIT cells causes a significant decrease in electrophoretic mobility but only the 3T3MIT cells show an increase in spontaneous aggregation. An increase in spontaneous aggregation of 3T3MIT cells is seen after growth in 200 mM urea for 18 h but no change in net surface charge occurs. The distribution of anionic sites on the membranes of cells was determined using the ultrastructural marker polycationized ferritin. The distribution of polycationized ferritin-binding sites was essentially identical for both cell lines under all conditions when they were labelled at 4 degrees C. When the cells were labelled with polycationized ferritin at 37 degrees C it was found that cells which have a high net rate of spontaneous aggregation also show rearrangement of anionic sites on their surface membrane. Clustering and rearrangement of anionic sites at 37 degrees C correlate with high rates of spontaneous aggregation.