Molecular species of lecithins from erythrocytes and plasma of man.

The lecithins of the plasma and erythrocytes of man were isolated by thin-layer chromatography, and the major molecular species were identified and quantitatively estimated by combined thin-layer and gas-liquid chromatography and specific enzymic hydrolyses. Using these techniques we could identify over 60 molecular species, accounting for some 98% of the total lecithin, in both plasma and cells, but only about 30 of them occurred in concentrations over 1%. The molecular species of lecithins in the cells and plasma were qualitatively similar; quantitatively, large differences were noted among and within the various classes of unsaturation. In the same blood, the erythrocyte lecithins contained 8-20 times as high a percentage of saturated lecithins and nearly twice as high a percentage of monounsaturated lecithins as did plasma lecithins. The differences in the relative amounts of a particular molecular species within a class of unsaturation were, however, most pronounced among the polyunsaturated lecithins. These results suggest that plasma and red cells possess distinct lecithin populations and that complete equilibration of the intact molecules between the two media is unlikely.