Arachidonic acid transfer from diacyl-sn-glycero-3-phosphocholine to ether phospholipids in rat peripheral blood...

The main phospholipid fractions of rat peripheral blood lymphocytes consisted of 30.8% diacylglycerophosphocholine and 20.3% diacylglycerophosphoethanolamine; the proportion of the ether phospholipids were small especially of alkyl- and alkenyl-glycerophosphoethanolamine (3.3 and 6.6% respectively). Other classes of phospholipids included glycerophosphoserine (10.5%), glycerophosphoinositol (6.5%) and sphingomyelin (13.6%). The incorporation of labeled arachidonic acid in the glycerophospholipids showed a rapid uptake into diacyl and ether classes of phospholipids and into triglycerides. When labeled cells were reincubated without arachidonic acid the diacylglycerophosphocholine rapidly lost its radioactivity, but a concomitant increase was observed in alkylacylglycerophosphocholine and more especially in alkenylacylglycerophosphoethanolamine and a smaller increase in alkyl- and diacyl-glycerophosphoethanolamine. The radioactivity was fairly constant in glycerophosphoserine and in glycerophosphoinositol, but decreased slightly in triglycerides. The arachidonic acid transfer reaction was completed after 2-3 hours reincubation. When labeled cells were reincubated in the presence of sodium cholate, the loss of radioactivity in the diacylglycerophosphocholine fraction increased. The transfer of arachidonic acid to ether phospholipids was the same with or without sodium cholate, but the later enhanced arachidonic acid transfer to diacylglycerophosphoethanolamine.