Effects of nonionic amphiphiles at sublytic concentrations on the erythrocyte membrane

The interactions of octaethyleneglycol alkylethers (C10-C16), pentaethyleneglycol dodecylether, and dodecyl D-maltoside with the human erythrocyte membrane were studied. All the amphiphiles protected erythrocytes against hypotonic haemolysis. At concentrations where the amphiphiles protected erythrocytes against hypotonic haemolysis they reduced phosphate efflux. The potency of the amphiphiles, at equiprotecting concentrations, was correlated negatively to the length of the alkyl chain. Potassium fluxes were increased by all the amphiphiles at protective concentrations. The relative potency of the amphiphiles varied but it was not simply related to the length of the alkyl chain. The only amphiphile affecting active potassium influx was octaethyleneglycol decylether which induced a slight decrease. It is concluded that the increase in passive cation fluxes caused by the amphiphiles is due to an increased permeability of the lipid bilayer induced through a nonspecific interaction of the amphiphiles with the bilayer. The effect of the amphiphiles on ion transport mediated by membrane proteins is proposed to be due to an alteration of the state of the transporting protein.