Interactions of surface-active alkyltrimethylammonium salts with the plasma membrane of Acanthamoeba castellanii.

The interactions of three surface-active alkyltrimethylammonium salts (C12-C16) with the plasma membrane of Acanthamoeba castellanii were studied. The surfactants caused a release of K+ from the cells at premicellar concentrations. The lytic effectiveness of the surfactants increased with an increase in the length of the alkyl chain with about an order of magnitude for every two carbon atoms added to the alkyl chain. Binding studies with the C16 homologue revealed that at a concentration corresponding to 50% release of K+ there were about 1.9 x10(10) molecules bound per cell. At prelytic concentrations the surfactants stimulated phagocytosis and pinocytosis. The mode of action of the surfactants on the plasma membrane of Acanthamoeba castellanii is discussed and it is hypothesized that the stimulation of endocytosis is due to a "fluidizing" effect of the surfactants on the lipid bilayer of the plasma membrane.