1. The fatty acid composition of the cholesterol esters, triglycerides and lecithin components of the major plasma lipoprotein classes was determined before and after the intravenous infusion of a linoleate preparation into a patient with essential fatty acid deficiency.
2. Marked differences developed between the fatty acid composition of the cholesterol esters of very-low-density lipoprotein (VLDL) on the one hand and of low- and high-density lipoproteins (LDL and HDL) on the other hand.
3. The data suggest that the infused linoleate was selectively incorporated into LDL and HDL cholesterol esters by the action of plasma lecithin-cholesterol acyltransferase, after prior incorporation into lipoprotein lecithin. In contrast, there was no rise in the linoleate content of VLDL cholesterol esters, which probably originated in either the liver or the small intestine.
4. These findings support the concept that plasma cholesterol esters are heterogeneous.