Lipids of cultured hepatoma cells: II. Effect of media lipids on cellular phospholipids

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Abstract
Minimal deviation hepatoma cells were cultured in a modified Swim's 77 medium supplemented with decreasing amounts of serum, lipid‐free serum, and lipid‐free serum containing added palmitic or linoleic acids. Cellular phospholipids were extracted and the class distribution determined quantitatively. The fatty acid composition of each phospholipid class was determined, and the percentages from cells grown on each of the various media were compared. Cellular phospholipid class and fatty acid compositions differed from media compositions, indicating that intact serum phospholipids are not incorporated into cellular structures. Phosphatidylcholine percentages decreased as the media serum and lipid levels decreased, while phosphatidylinositol and phosphatidylethanolamine percentages increased. Sphingomyelin of cells grown in medium containing added linoleic acids contained a high level of a 24∶2 acid. All classes, except sphingomyelin, contained elevated levels of 18∶1 acid and decreased levels of polyunsaturated fatty acids, relative to normal rat liver. Cells cultured on lipid‐free medium did not contain increased concentrations of 20∶3 acid, suggesting that this hepatoma cell cannot desaturate monoenoic acids. Phosphoglycerides of cells, grown on lipid‐free medium, had the highest monoene fatty acid concentration, whereas those cells grown on media containing added linoleic acid had the lowest concentrations, suggesting that linoleate may inhibit or regulate monoenoic acid biosynthesis in this cell. These mass data also demonstrate that monoenoic fatty acid biosynthesis in this cultured hepatoma cell responds to dietary changes.