Esterification of 8,11,14-eicosatrienoate and arachidonate into alkylacyl- and diacylglycerophosphocholine by vascular endothelial cells.
Agonist-stimulated phospholipases release arachidonate, but not 8,11,14-eicosatrienoate, from human endothelial cells. One source of the arachidonic acid is deacylation of 1-alkyl-2-arachidonoyl-glycerophosphocholine, with subsequent conversion of some of the resultant lysophospholipid to platelet-activating factor. This study has compared the distribution of incorporated 8,11,14-[14C]eicosatrienoate in alkylacyl-GPC and diacyl-GPC with that of [14C]arachidonate synthesized endogenously by desaturation of the 8,11,14-[14C]eicosatrienoate. Cells were incubated for 24 or 48 hr with 8,11,14-[14C]eicosatrienoate, and the resultant mixture of 14C-fatty acids in the cellular lipids was characterized by gas chromatography. The choline phospholipids were then separated, hydrolyzed with phospholipase C and derivatized to diradylbenzoates. Gas chromatographic analysis indicated extensive incorporation of [14C]eicosatrienoate, as well as [14C]arachidonate, into alkylacyl-GPC. Although the ratio of esterified [14C]arachidonate to [14C]eicosatrienoate was greater in alkylacyl-GPC than in diacyl-GPC, the enrichment with [14C]arachidonate was far less than the ratio of arachidonate/eicosatrienoate released from these cells. These results thus support the hypothesis that the acyl specificity of polyunsaturated fatty acid release is provided by the agonist-stimulated phospholipase A2 rather than the composition of the alkylacyl-GPC.
Rosenthal
M D
MD
Dept. of Biochemistry, Eastern Virginia Medical School, Norfolk, VA 23501.
Brown
M E
ME
Jones
J E
JE
D015126:8,11,14-Eicosatrienoic Acid / Q000378:metabolism*; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism*; D004951:Esterification; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D006801:Humans; D010713:Phosphatidylcholines / Q000096:biosynthesis; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010972:Platelet Activating Factor / Q000096:biosynthesis
D001095:Arachidonic Acids; D005231:Fatty Acids, Unsaturated; D010713:Phosphatidylcholines; D010972:Platelet Activating Factor; D016718:Arachidonic Acid; D010741:Phospholipases A; D054467:Phospholipases A2; D015126:8,11,14-Eicosatrienoic Acid