Differences in positional esterification of 14,15-epoxyeicosatrienoic acid in phosphatidylcholine of porcine coronary artery endothelial and smooth muscle cells.
Epoxyeicosatrienoic acids (EETs) are readily incorporated into phospholipids of smooth muscle cells (SMC) and endothelial cells (EC). Incorporation of EETs into intact porcine coronary arteries potentiates EC-dependent relaxation, but not vasorelaxation induced by agents that act solely on SMC. To explore the potential mechanisms responsible for this difference, porcine coronary artery SMC and EC preloaded with [3H]14,15-EET were treated with calcium ionophore A23187. Although the amount of EET incorporated into EC and SMC was similar, A23187 stimulated a five-fold increase in release of radioactivity from EC, but only a 21% increase in release from SMC. Thin layer chromatography (TLC) examination of cell lipids demonstrated that > 70% of the incorporated radioactivity was present in phosphatidylcholine (PC) in both SMC and BC. After treatment of EC PC with PLA2, TLC analysis indicated that approximately equal to 75% of radioactivity was present as free EET, and 25% of radioactivity was present as lyso-PC. Therefore, most of the 14,15-EET was esterified into the sn-2 position of PC in EC. However, in SMC, approximately equal to 70% of radioactivity was present as lyso-PC after PLA2 treatment, indicating that the EET was predominately esterified into the sn-1 position. In contrast, all of the 14,15-EET was esterified into the sn-2 position of PI in both EC and SMC. These results suggest that the preferential incorporation of 14,15-EET into the sn-1 position of PC in SMC may help to explain the greater retention of the compound in SMC, while incorporation into the sn-2 position of PC in EC may facilitate agonist-induced 14,15-EET release and potentiation of EC-dependent porcine coronary artery relaxation.
Fang
Xiang
X
Department of Biochemistry, University of Iowa College of Medicine, 4-403 BSB, Iowa City, IA 52242, USA. xiang-fang@uiowa.edu
Weintraub
Neal L
NL
Spector
Arthur A
AA
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002478:Cells, Cultured; D003331:Coronary Vessels; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D004951:Esterification; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism*; D013552:Swine; D014316:Tritium; D014665:Vasodilator Agents / Q000494:pharmacology*
D010713:Phosphatidylcholines; D014665:Vasodilator Agents; D014316:Tritium; D000001:Calcimycin; C046782:14,15-epoxy-5,8,11-eicosatrienoic acid; D015126:8,11,14-Eicosatrienoic Acid