Interactions of Surface-active Alkyltrimethylammonium Salts with the Plasma Membrane of Acanthamoeba castellanii

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Abstract
The interactions of 3 surface-active alkyltrimethylammonium salts (C12-C16) with the plasma membrane of A. 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 2 C atoms added to the alkyl chain. Binding studies with the C16 homolog revealed that at a concentration corresponding to 50% release of K+ there were about 1.9 .times. 1010 molecules bound/cell. At prelytic concentrations the surfactants stimulated phagocytosis and pinocytosis. The mode of action of the surfactants on the plasma membrane of A. castellanii is discussed and the stimulation of endocytosis may be due to a fluidizing effect of the surfactants on the lipid bilayer of the plasma membrane.