Lipid composition of normal male rat islets.

Lipid composition was studied in fresh isolated islets from normal male rats. Extractable lipids represent 1856 micrograms per mg islet protein. In such extracts, phospholipids and neutral lipids represent 13.5% and 86.5%, respectively. Phosphatidylcholine (45.8%) and phosphatidylethanolamine (20.6%) were the major components of the phospholipid fraction, and phosphatidylinositol (8.9%) was the minor component. Esterified cholesterol (38.5%), cholesterol (25.5%) and free fatty acids (24.4%) were the major components of the neutral lipid fraction. Fatty acids esterified to phospholipids account for 619.7 pmol/islet, and 2710 pmol/islet were esterified to neutral lipids. In the phospholipid fraction, saturated and unsaturated fatty acids were in a similar proportion. Conversely, in the neutral lipids, two-thirds of the fatty acids were unsaturated. The omega 6 family was the main component of the phospholipid unsaturated fatty acids. In the omega 6 and omega 3 families, the long-chain fatty acids represent the main components. In the neutral lipid fraction, a different percentage of each family was found: omega 3 greater than omega 6 greater than omega 9. The long-chain polyunsaturated fatty acids were also predominant species in the omega 6 and omega 3 families. Further studies on the lipid composition of islets, obtained from rats with normal and altered islet functions, could provide new insights into the knowledge of the mechanism of insulin secretion.