Transfer of steroids and alpha-tocopherol between liposomal membranes.

The transfer of various steroids and alpha-tocopherol between liposomes was examined. The transfer rate of cholest-4-en-3-one and epicholesterol between egg yolk phosphatidylcholine liposomes was much higher than that of cholesterol. Rapid transfer was also noted for coprostanol and 5-cholesten-3 beta-ol-7-one, while the transfer of cholestanol, which has a 3 beta-hydroxyl residue and a planar nucleus structure, was similar to that of cholesterol. These results suggest that the mode of interaction between steroid and phospholipid may be an important factor controlling the rate of transfer. It was found that alpha-tocopherol could also be transferred between liposomes. The transfer rate of alpha-tocopherol was dependent on the temperature and the phospholipid composition.