Effects of ethanol on permeability of phosphatidylcholine/cholesterol mixed liposomal membranes

Effects of ethanol on permeability of large unilamellar vesicles (about 170 nm in diameter), composed of a dipalmitoyl phosphatidylcholine (DPPC)/cholesterol binary mixture, were studied by monitoring leakage of a fluorescent dye, calcein, entrapped in the inner aqueous phase of the vesicles. In the presence of 25 mol% cholesterol, the leakage was dramatically increased, and the permeability at 1.0 M ethanol was about eight times larger than that without ethanol and cholesterol. This effect of ethanol on the membrane permeability was similar to our previous findings concerning mixed membranes of dilauroyl phosphatidylethanolamine and DPPC (H. Komatsu and S. Okada (1996) Biochim. Biophys. Acta 1283, 73-79). It was suggested that the presence of ethanol can lead to high permeability even if the membranes are stable and have a low permeability in its absence. Copyright (C) 1997 Elsevier Science Ireland Ltd.