Effects of membrane stabilizing agents and radiation on liposomal membranes.

Effects of membrane stabilizing agents cholesterol and cepharanthin on radiation-induced lipid peroxidation and permeability were studied, together with an examination of changes in membrane properties by radiation. Radiation-induced lipid peroxidation caused an increase in membrane permeability in liposomes. Although cholesterol and cepharanthin caused a decrease in the degree of permeability, lipid peroxidation tended to increase in the presence of cholesterol in contrast to a decrease in the presence of cepharanthin. The ESR studies on irradiated liposomes suggest that the membrane stabilizing effect of cholesterol may be dependent on the rigidification of membranes, not on the stimulation of lipid peroxidation. On the other hand, cepharanthin suppressed membrane permeability mainly by inhibiting the radiation-induced lipid peroxidation.