Incorporation of fatty acids into phosphatidylcholine is reduced during storage of human erythrocytes: Evidence for distinct lysophosphatidylcholine acyltransferases

The incorporation of [1-C-14]palmitic or [1-C-14]oleic acid into phosphatid ylcholine and the effect on blood group antigen expression were examined in human erythrocytes stored at 4 degreesC for 0-3 weeks. Blood drawn into ED TA was obtained by venepuncture from healthy volunteers. A 50% suspension o f washed erythrocytes was incubated in buffer containing [1-C-14]fatty acid for up to 60 min at 37 degreesC with moderate shaking. Phosphatidylcholine was extracted and analyzed for uptake of radiolabelled fatty acid and phos pholipid phosphorus content. Incorporation of [1-C-14]palmitic or [1-C-14]o leic acid into phosphatidylcholine was reduced during storage. The mechanis m for the reduction in radiolabelled fatty acid incorporation into phosphat idylcholine was a 64% (p < 0.05) reduction in membrane phospholipase A(2) a ctivity. Although human erythrocyte membranes isolated from freshly drawn b lood are capable of reacylating lysophosphatidylcholine to phosphatidylchol ine, with storage, a markedly different substrate preference between palmit oyl-Coenzyme A and oleoyl-Coenzyme A was observed. Lysophosphatidylcholine acyltransferase activity assayed with oleoyl-Coenzyme A was unaltered with storage. In contrast, lysophosphatidylcholine acyltransferase activity assa yed with palmitoyl-Coenzyme A was elevated 5.5-fold (p < 0.05). Despite the se changes, storage of erythrocytes for up to 3 weeks did not result in alt ered expression of the various blood group antigens investigated. We conclu de that the incorporation of palmitate and oleate into phosphatidylcholine is dramatically reduced during storage of human erythrocytes. The observed differential in vitro substrate utilization suggests that distinct acyltran sferases are involved in the acylation of lysophosphatidylcholine to phosph atidylcholine in human erythrocytes.