Lipid composition of the matrix of human submandibular salivary gland stones.

The lyophilized stone matrix, prepared by exhaustive dialysis of pulverized stones against 10 per cent EDTA and water, yielded 9.6 +/- 0.9 mg per cent of lipids. Following fractionation of the lipid extract on silicic acid columns, 57 per cent of lipids were found in the neutral lipid fraction, 40 per cent in the glycolipid fraction and 3 per cent in the phospholipid fraction. Of the total neutral lipids, 77.3 per cent were represented by free fatty acids, 14.7 per cent by cholesterol, 4.1 per cent by triglycerides and 3.2 per cent by cholesterol esters. The glycolipid fraction was comprised of simple glycosphingolipids (11.3 per cent), mainly lactosyl- and glucosylceramides, and of neutral and sulphated glyceroglucolipids (88.7 per cent). The sulphated glyceroglucolipids consisted of tri- and tetraglucosyl glyceroglucolipids, whereas hexa- and octaglucosyl glyceroglucolipids were the predominant constituents of the neutral glyceroglucolipid fraction. The phospholipids exhibited a high content of sphingomyelin (22.3 per cent), phosphatidylcholine (12.1 per cent), phosphatidylethanolamine (11.4 per cent), phosphatidylserine (10.5 per cent) and lysophosphatidylcholine (13.3 per cent). The major fatty acids of the neutral lipid fraction were hexadecanoate, octadecanoate and octadecenoate. The glycolipids contained large quantities of hexadecanoate and tetracosanoate, while the hexadecanoate, octadecanoate and tetracosanoate were the principal fatty acids of the phospholipid fraction.