Lipid Composition and Lipid Synthesis in Guinea Pig Megakaryocytes and Platelets

Lipid composition and lipid synthesis have been compared in guinea pig megakaryocytes and platelets. Megakaryocytes were isolated from guinea pigs to 85% purity. Lipids were extracted and were separated by thin layer chromatography. Phospholipid (PL) content was determined by measurement of lipid phosphorus, and cholesterol and fatty acids were quantitated by gas-liquid chromatography. PL composition of megakaryocytes was:PS + PI 15.2%; SM 14.0%; PC 40.1%; PE 30. 6%. PL composition of platelets was: PS 10.1%; PI 4.5%; SM 16.5%; PC 39.5%; PE 29.6%. The cholesterol:PL ratio was 0.35 for megakaryocytes and 0.55 for platelets. The major fatty acids in the PL were: (% of total)Megakaryocytes and platelets were incubated for 1.5 hr with 14C-acetate. Megakaryocytes incorporated acetate into cholesterol and other sterols, ceramide, and PL (0.060, 0.016 and 0.012 nmoles/105 cells). Platelets incorporated acetate into ceramide and PL (0.02 and 0.06 nmoles/109 cells) but only trace amounts into sterols. There appears to be active biosynthesis of cholesterol in megakaryocytes but not in platelets.