Utilization of exogenous linolenic and oleic acids for plasma membrane phosphoglyceride systhesis in L-Fibroblasts

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The inability of the strain L-fibroblast to synthesize quatitatively significant amounts of polyenoic fatty acid and the apparent lack of turnover of their phosphoglyceride acyl groups under the usual conditions of cell culture makes them especially well suited for studies concerning the effect of fatty acid unsaturation on biological membranes. Such cells grown in the absence of exogenous lipid sources have in their phosphoglycerides only traces of polyenoic fatty acid. By infusing fatty acid supplements into suspension cultures of logarithmically growing cultures of L-fibroblasts it is possible to increase singnificantly their phosphoglyceride polyenoic fatty content to as much as 50% of the total lipid phosphoglyceride fatty acids. The infusion of fatty acid supplements at a constant rate over a 48 h time period diminishes the toxic effects which may accompany single doses of unesterified fatty acid and reduces considerably the accumulation of cytoplasmic lipid droplets. Cultures supplemented in this way have virtually the same generation times as non-supplemented control cultures. The data show that alterations in surface membrane and homogenate polyenoic fatty acid composition are minimal when oleic acid is supplied to the culture. During exposure to large amounts of polyenoic fatty acid, however, the unsaturation of plasma membrane total phosphoglyceride fraction is less than that of the cell homogenate. This effect is more pronounced in the phosphatidylethanolamine than in the phosphatidylcholine fraction.