The consequences of incubating liposomes with rat thymocytes have been studied using liposomes of dipalmitolyphosphatidylcholine and cholesterol or dipalmitoylphosphatidylcholine only. 2. Dipalmitoylphosphatidylcholine-cholesterol liposomes do not bind to the cells can be removed by washing. An increase in cellular cholesterol is observed. However dipalmitoylphosphatidylcholine liposomes bind rapidly to the cells and cannot be removed by repeated washing. Cholesterol is removed from the cells. 3. There are small changes in intracellular cations in the cholesterol-enriched cells, but no transport studies have been made. Cells depleted of cholesterol lose K+ with little change in intracellular Na+. Na+ influx is increased. The majority of this increase appears to be ouabain-sensitive, indicating in pump-mediated Na+ influx. K+ influx is reduced. 4. The significance of these results is discussed.
