Characterization and quantification of red cell lipids in normal man

Human red cell lipids have been studied in a series of normal individuals. Cholesterol comprises 25% of total red cell lipid, and free fatty acid is present. Evidence is presented that the total amount of lipid phosphorus per average red cell is 1.40 × 10−11 mg and that most extraction procedures fail to extract 8% or more (some as much as 40–50%) of red cell phospholipid.The average percentage distribution of the individual phospholipids was: choline glycerophosphatides 30% sphingomyelin 24%, ethanolamine glycerophosphatides 26%, and serine glycerophosphatides 15%. Other minor phospholipid components were also identified. The normal range for total red cell plasmalogen was found to be 4.65–5.85 × 10−11 μmole/cell. Evidence for the presence of a carbohydrate-containing lipid which was eluted from silicic acid columns with serine and inositol glycerophosphatides is also given.The fatty acid distribution of each major phospholipid fraction is characteristic. Ethanolamine glycerophosphatides are high in 20:4, 22:5, and 22:6, while serine and inositol glycerophosphatides contain large amounts of 18:0 and 20:4. Lecithin is distinguished by 20–25 moles % 18:2 and sphingomyelin by high concentrations of 24:0 and 24:1.