Remodeling of arachidonate-containing phosphoglycerides within the human neutrophil

Initial incorporation and subsequent remodeling of 16 phosphoglyceride molecular species containing arachidonate in the human neutrophil have been studied. Neutrophils were pulse-labeled with [³H]arachidonic acid (AA) for 5 min, then phospholipids were analyzed either at this time point or after a subsequent 120-min incubation. [³H]AA was found to be incorporated into phosphoglycerides phosphatidylinositol (PI) > phosphatidylcholine (PC) > phosphatidylethanolamine (PE) by 5 min. Incorporation of [³H]AA was not related to pool size, but reflected an increase in phosphoglyceride turnover. Following the 120-min incubation, only PE gained a significant amount of labeled arachidonate. Specific activity analysis revealed that PI contained the highest labeled/unlabeled ratio at both 5 min and 120 min. After the initial 5-min pulse, the majority of [³H]arachidonate was incorporated into 1-acyl-2-[³H]arachidonoyl-sn-glycero-3-PC, -PE, and -PI showing no preference for fatty acyl chains at the sn-1 position. However, [³H]AA was remodeled into 1-alkyl-acyl- and 1-alk-1-enyl-acyl-sn-glycero-3-PC and -PE molecular species in those neutrophils incubated for the additional 120 min. Specific activities of [³H]AA within all diacyl molecular species were initially higher relative to those of alkyl-acyl and alk-1-enyl-acyl molecular species, but for PC and PE became more uniform as label shifted into ether and plasmalogen pools during the additional 120-min incubation. In contrast, the specific activity of 1-stearoyl-2-arachidonoyl-sn-glycero-3-PI remained constant throughout the 120-min incubation.