Sodium ion diffusion through liposome membranes containing cerebroside.

Na+ efflux from liposomes (small unilamellar vesicles, SUV) of various compositions was studied, using 22Na+ and 3H-labelled stachyose in simultaneous dual isotope measurements, stachyose being used as a measure of liposome disintegration. Dialysis was utilised to separate liposomes from extra-liposomal activity. Liposomes were made from egg lecithin and sphingomyelin and from mixtures of egg lecithin, sphingomyelin, cerebroside, sulphatide and cholesterol. All mixtures produced more leaky and less stable SUVs than pure lecithin and pure sphingomyelin. The incorporation of cerebroside is significantly smaller than that of the phospholipids including sphingomyelin. It was found that membranes containing cerebroside had a significantly higher Na+ permeability than membranes without cerebroside.