Role of electric surface charge of cell membrane in phagocytosis

An attempt to clarify the role of surface charge on cell membrane was performed on two cell types, phagocytic (rat peritoneal macrophage) and non-phagocytic cells (Ehrlich ascites tumor cell). The electrophore-tic mobility of both cells was remarkably reduced by the treatment with protamine sulfate, and diminished considerably by the increase of ionic strength in electrophoretic medium. Both cells were aggregated into small clumps in varying size by the treatment with protamine sulfate. Such a decrease of negative electric charge density on the cell surface resulted in active phagocytosis. Even in non-phagocytic cells phagocytosis occurred after the treatment with protamine sulfate. In contrast, no significant difference in phagocytic activity was observed between chondroitin sulfate-treated and untreated cells. Under the electron microscope the cells of both types incubated in the medium with the addition of protamine sulfate showed numerous bizarre and irregular cytoplasmic projections, while no particular feature was observed after treatment with chondroitin sulfate. In protamine sulfate-treated cells, many particulate substances were usually found attaching to the cell membrane. In the medium without ionic substance, particle attachment on the cell surface was hardly observed in the cells of both types. Therefore it was strongly suggested that the electric charge density on the cell surface was at least one of the factors responsible for the attachment of the particle to the cell.