Lipids of cultured hepatoma cells: I. Effect of serum lipid levels on cell and media lipids

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Abstract
Minimal deviation hepatoma cells were cultured as monolayers to confluency in roller flasks containing modified Swim's medium, supplemented with decreasing amounts of serum, lipid‐free serum, and lipid‐free serum containing added fatty acids. Good cell growth was observed until serum levels fell below 5% of the medium. Media containing lipid‐free serum or lipid‐free serum plus linoleic or palmitic acids did not support good growth. Lipids were extracted from cells; media, obtained during the first and last half of the incubation period, resolved into neutral and phospholipid fractions; fatty acid composition of each fraction analyzed by gas liquid chromatography; and lipid class distributions compared by thin layer chromatography. The data showed that the media contained more neutral lipids and phospholipids after incubation than initially, indicating that minimal deviation hepatoma cells excreted lipids into the media. The class composition of the excreted lipids resembled that of the serum. A comparison of media, cells, and serum fatty acid compositions indicated that the lipids secreted into the media were of cellular origin. Although some differences were noted, in general, cells grown on the nine different media had the same ca. neutral lipid and phospholipid class and fatty acid compositions. In contrast, dramatic differences were observed in the class and fatty acid compositions of the serums from that of the cells and media. These results indicate that exogenous serum lipids had little influence on cellular class and fatty acid compositions of the minimal deviation hepatoma cells. This neoplasm did not contain detectable levels of glyceryl ether diesters, indicating that this compound is not characteristic of all tumors. Lipid class profiles and fatty acid compositions of cells grown on various media suggest that the minimal deviation hepatoma cells can synthesize most, if not all, neutral lipid and phosphoglyceride classes found in liver.