Lipids of cultured hepatoma cells: VII. Structural analyses of glycerolipids in minimal deviation hepatoma 7288C.

Phosphatidylcholine. phosphatidylethanolamine, and triglycerides were isolated from minimal deviation hepatoma 7288C cells cultured as monolayers to confluency in roller flasks containing Swim's 77 medium supplemented with 5% fetal calf serum, plus 20%, 10%, or 5% bovine serum. Fatty acid distribution at each position of glycerol was determined for the 3 glycerolipid classes, and carbon number distributions of triglycerides and diglycerides derived from phosphatidylcholine and phosphatidylethanolamine were quantitated by high temperature gas liquid chromatography. Fatty acid composition was only marginally affected by the level of bovine serum in the culture medium. Percentage composition of fatty acids esterified at each position of the 3 glycerolipids was different, indicating a nonrandom distribution of acyl groups in triglycerides and the 2 diacyl phosphatides. The carbon number distribution of diglycerides derived from phosphatidylcholine and phosphatidylethanolamine was different, and neither carbon number distribution agreed with the calculated 1-random, 2-random diacyl distribution, thus indicating pairing of certain acids in the diglycerides derived from these phospholipd classes. The determined triglyceride carbon number distributions did not show complete agreement with those calculated, assuming a 1-random, 2-random, 3-random type of fatty acyl distribution, suggesting preferential pairing of some acids in this lipid class. The 1-, 2-diglycerides derived from phosphatidylcholine, phosphatidylethanolamine, and triglycerides differed, indicating either selectivity in utilization of diglyceride species in biosynthesis of these glycerolipids, or modification of glycerolipids after their initial synthesis.