Lipid Content and In Vitro Incorporation of Free Fatty Acids Into Lipids of Human Platelets: The Effect of Storage at 4°C

Lipid content and capacity to incorporate in vitro palmitate-1-¹⁴C and linoleate-1-¹⁴C into lipids was investigated in fresh and stored (4°C) human platelets. Cholesterol and phospholipids decreased 30% during storage for 6 days. Molar ratio of cholesterol to phospholipids and percentage distribution of individual phospholipids were similar in fresh and stored platelets. Palmitate bound to albumin was rapidly transferred by an energy-independent mechanism into a free fatty acid fraction of platelets. From there it was incorporated into glycerides and phospholipids, a process requiring energy. More palmitate than linoleate was incorporated into fatty acids and glycerides of fresh and stored platelets but linoleate exceeded palmitate in its incorporation into phosphatidylethanolamine. Storage of platelets produced the following changes: (1) Incorporation of palmitate into total lipids was significantly reduced but not that of linoleate. (2) Both palmitate and linoleate showed increased incorporation into phosphatidylethanolamine. (3) Incorporation of linoleate into free fatty acids and triglycerides and of palmitate into phosphatidylcholine was reduced.