Lipid components of two different regions of an intestinal epithelial cell membrane of mouse

1. The lipid compositions of the two different regions of the plasma membrane of mouse intestinal epithelial cells i.e., microvillus membranes and basolateral membranes, were analysed. They showed very different compositions. Microvillus membranes were rich in cholesterol and glycolipids but poor in phospholipids as compared with basolateral membranes and other types of plasma membranes. The total lipid content per 100 mg protein was 61.5 mg in microvillus membranes and 95.2 mg in basolateral membranes. The microvillus membrane contained 16.0 mg of phospholipids and 29.0 mg of glycolipids per 100 mg protein, and the basolateral membrane contained 58.6 mg of phospholipids and 12.4 mg of glycolipids per 100 mg protein. The molar ratio of cholesterol, phospholipid and glycolipid was 1:1:1 in microvillus membranes and 1:2.5:0.3 in basolateral membranes. 2. The major neutral lipids were cholesterol and free fatty acids in both membranes. 3. The major phospholipids of microvillus membranes were phosphatidylethanolamine (49.0%) and phosphatidylcholine (25.1%), which were also predominant in basolateral membranes but reversed in the relative amount; phosphatidylcholine (51.0%) and phosphatidylethanolamine (27.4%). 4. There were considerable differences between the molar ratio of fatty acid components of the two membranes: 16:0 (13.6%), 18:0 (28.0%), 18:2 (28.4%) for microvillus membranes and 16:0 (19.7%), 18:0 (22.7%), 18:2 (31.6%) for basolateral membranes. The minor components showed very similar relative amounts. 5. The major glycolipids were ceramide monohexoside and probably globoside in both membranes. 6. These results were obtained from membrane preparations from animals of ICR strain kept on an enriched artificial diet originally designed for enhancing reproduction. When animals of dd strain were fed a simple growth diet, it was found that the phospholipids of the two membrane preparations broke down considerably during the length of time necessary for preparation procedures.