Alterations in lipid composition of liver cell plasma membranes during development.

Liver plasma membranes of Swiss-Webster CFW mice ranging in age from 5 to 165 days were isolated employing a two-phase dextran/polyethylene glycol polymer system. Electron microscopy revealed low mitochondrial and microsomal contamination. Lipids were quantitatively extracted and subjected to two dimensional thin layer chromatography. Individual lipids were eluted and phosphorus was measured by the Malachite green method. Cholesterol was quantitated by the micro Liberman-Burchard method and sphingolipids were quantitated fluorometrically with fluorescamine. During development, phosphatidylethanolamine levels decreased from 43.2% to 19.5% whereas phosphatidylcholine levels rose from 26% to 45.2%. The ration of phospholipid/cholesterol remained essentially constant during development; but the sphingolipid/cholesterol and sphingolipid/phospholipid ratios increased from 0.75 to 1.79 and 0.11 to 0.34, respectively.