A comparative study of the lipids of chylomicron membrane and fat core and of the lymph serum of dogs.

Thoracic lymph was collected from 13 dogs fed corn oil and butterfat. The chylomicrons were isolated by centrifugation. The lipid composition of the fat core and the membrane of the chylomicron was compared to that of the surrounding lymph serum. The fat cores contained 90-96% triglyceride, 0.7-1.9% free cholesterol, 0.2-0.5% steryl ester, 0.9-3.5% free fatty acid and 1.4-6.1% diglyceride, but no phospholipid. The lipids of the membranes contained 58-75% phospholipid, 20-35% triglyceride, 2-5% free cholesterol, 1-2% free fatty acid, and 2-3% diglyceride, but little or no steryl ester. The membrane phospholipids were made up of 70-90% lecithin, 5-20% phosphatidyl ethanolamine, and 1-3% each of lysolecithin and sphingomyelin. The lymph serum contained 24-47% of total lipid as phospholipid, of which 70-92% was lecithin; the phosphatidyl ethanolamine, lysolecithin and sphingomyelin also present contributed 1-10% each. The neutral lipids of the lymph serum contained 49-75% triglyceride, 2-15% free cholesterol, 6-23% esterified cholesterol, 10-33% free fatty acid and 1-6% diglyceride.Alterations in dietary fat, or plant sterol supplementation led to lesser changes in the lipids of the chylomicron membranes than in the lipids of any other lymph fraction. The least variation was seen in the phospholipids.