Altered red cell membrane fluidity during schizogonic development of malarial parasites (Plasmodium falciparum and P. lophurae).

The plasma membranes of human or duckling erythrocytes infected with malarial parasites (Plasmodium falciparum and P. lophurae respectively) were stained by the fluorescent dye merocyanine 540 in the presence of serum. Unparasitized erythrocytes from infected ducklings or from in vitro cultures remained unstained in the presence of serum. Because merocyanine 540 has a greater affinity for fluid phased or disordered lipid bilayers the results suggest that upon infection of the red blood cell the erythrocyte plasma membrane becomes disordered or is increased in its fluidity. Such alterations of the host erythrocyte are probably due to parasite-induced modifications in the underlying spectrin network (required for lipid leaflet asymmetry) as well as changes in erythrocyte membrane lipid composition.