Changes in the Incorporation of Free Fatty Acids Upon the Stimulation of Human Polymorphonuclear Leukocytes

We have investigated the incorporation of free fatty acids into the cellular lipids of human polymorphonuclear leukocytes (PMN). Resting PMN incorporated both saturated and unsaturated fatty acids into triacylglycerol with only small amounts incorporated into the phospholipids. In contrast, PMN stimulated with the calcium ionophore A23187 incorporated significantly higher amounts of fatty acids, predominantly those other than arachidonic acid, into phosphatidylcholine and phosphatidylinositol, with reduced incorporation into triacylglycerol. Stimulation of PMN with serum-treated zymosan or the chemotactic peptide f-met-leu-phe but not phorbol myristate acetate, also increased the incorporation of fatty acids into these phospholipids. This stimulation-induced incorporation of fatty acids into cellular phospholipids was directed exlusively into position 2 of the lipid and probably reflects the reacylation of lysophospholipids after the release of arachidonic acid by phospholipase A2.