UPTAKE AND UTILIZATION OF FREE FATTY-ACIDS SUPPLIED BY LIPOSOMES TO MAMMARY-TUMOR CELLS IN CULTURE

Unesterified oleic acid was co-dispersed with various phospholipids in Ca-Mg-free saline and sonicated. Most of the fatty acid co-eluted with phospholipid vesicles when the sonicate was chromatographed on a column of Sepharose 4B. Cells from mouse mammary tumors, maintained in primary monolayer culture, were incubated with these phospholipid-oleic acid vesicles and optimal conditions for the uptake of oleic acid were established. When phosphatidylcholine and phosphatidylserine were used to make the vesicles, the oleic acid was taken up by cells more efficiently than was oleic acid complexed with albumin. The liposome-supplied unesterified oleic acid was rapidly incorporated into other cellular compounds, especially triglycerides and phospholipids. Growth of cells was measured after a 2-h pulse with the liposomes. The amount of DNA in treated cultures was 50% greater than in control cultures by 3 days after treatment. The magnitude of the growth response was sensitive to liposome dosage and to cell density in the treated cultures. This survey suggests that liposomes can be employed to insert materials directly into epithelial cells via their apical surface, that oleic acid so supplied is readily metabolized, and that solutes from liposomes can participate in functioning of the cells. © 1979.