Human neutrophils incorporate arachidonic acid and saturated fatty acids into separate molecular species of phospholipids

The incorporation of radiolabeled arachidonic acid and saturated fatty acids into choline-linked phospho-glycerides (PC) of rabbit and human neutrophils was investigated by resolving the individual molecular species by reversed-phase high performance liquid chromatography. PC from neutrophils incubated with a mixture of [₃H] arachidonic acid and [¹⁴Cjstearic or [¹⁴C]palmitic acid contains both radiolabeis; however, double labeling of individual molecular species is minimal. After labeling for 2 h, the [³H]arachidonate is distributed almost equally between diacyi and 1-O-alkyl-2-acyl species, but it is incorporated into diacyi species containing unlabeled stearate or palmitate at the sn-1 position. In contrast, labeled saturated fatty acids are incorporated only into diacyl species and contain predominantly oleate and linoleate at the sn-2 position. Labeled linoleate is not incorporated into ether-linked species, but is found in the same species as labeled stearate. The findings suggest that mechanisms exist in neutrophils for specific shunting of exogenous arachidonic acid into certain phospholipid molecular species and support the concept that the 1-O-alkyl-2-arachidonoyl species may be a functionally segregated pool of arachidonic acid within the PC of neutrophils.