To define aspects of lipid composition and bilayer asymmetry critical to barrier function, we
examined the permeabilities of liposomes that model individual leaflets of the apical
membrane of a barrier epithelium, Madin-Darby canine kidney type 1 cells. Using published
lipid compositions we prepared exofacial liposomes containing phosphatidylcholine,
sphingomyelin, glycosphingolipids, and cholesterol; and cytoplasmic liposomes containing
phosphatidylethanolamine, phosphatidylserine, and cholesterol. The osmotic permeability of …