Fatty acid composition of human plasma lipoprotein phosphatidylinositols.

Phosphatidylinositol (PI) was the only anionic phospholipid found consistently in human plasma lipoproteins. High density lipoproteins (HDL) contained a greater proportion of PI (2.6% of the phospholipids) than did either the low density (LDL) or the very low density (VLDL) lipoproteins (1.6 and 1.7%, respectively). Lipoprotein PI was enriched in stearic and arachidonic acids when compared to phosphatidylcholines from the same fractions. The fatty acid composition of the lipoprotein PI, although the same in all lipoprotein fractions, had less arachidonic acid than platelet PI and less palmitic acid than erythrocyte PI. The data suggest that significant exchange of PI between lipoproteins and cell membranes is not likely, whereas PI exchange among the different classes of lipoproteins is possible.