title: Liquid chromatographic-electrospray ionization-mass spectrometric analysis of cytochrome P450 metabolites of arachidonic acid.
abstract: Arachidonic acid (AA) can be metabolized by cytochrome P450 (CYP) enzymes to many biologically active compounds including 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids (EETs), their corresponding dihydroxyeicosatrienoic acids (DHETs), and 20-hydroxyeicosatetraenoic acid (20-HETE). These eicosanoids are potent regulators of vascular tone. We developed a liquid chromatography-electrospray ionization-mass spectrometry method to simultaneously determine 5,6-, 8,9-, 11,12-, and 14,15-EETs; 5,6-, 8,9-, 11,12-, and 14,15-DHETs; and 20-HETE. [2H8]EETs, [2H8]DHETs, and [2H2]20-HETE were used as internal standards. These compounds are readily separated on a C18 reverse-phase column using water:acetonitrile with 0.005% acetic acid as a mobile phase. The internal standards, [2H8]EETs, [2H8]DHETs, and [2H2]20-HETE, eluted slightly faster than the natural eicosanoids. The samples were ionized by electrospray with fragmentor voltage of 120 V and detected in a negative mode. The negative ion detection gave a lower background than the positive ion detection for these compounds. These eicosanoids exhibited high abundance of the ions corresponding to [M - 1]-. The m/z = 319, 337, and 319 ions were used for quantitation of EETs, DHETs, and 20-HETE, respectively. The detection limits using selected ion monitoring of these compounds are about 1 pg per injection. The position of functional groups and water content of mobile phase had a significant effect on the sensitivity of detection. Water content of 40% was found to give maximal sensitivity. The method was used to determine EETs, DHETs, and 20-HETE in bovine coronary artery endothelial cells, dog plasma, rat astrocytes, and rat kidney microsome samples.
authors.affiliation: Department of Pharmacology & Toxicology, Cardiovascular Research Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.
authors.forename: K
authors.initials: K
authors.lastname: Nithipatikom
authors.forename: A J
authors.initials: AJ
authors.lastname: Grall
authors.forename: B B
authors.initials: BB
authors.lastname: Holmes
authors.forename: D R
authors.initials: DR
authors.lastname: Harder
authors.forename: J R
authors.initials: JR
authors.lastname: Falck
authors.forename: W B
authors.initials: WB
authors.lastname: Campbell
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000032:analysis*; D001253:Astrocytes / Q000737:chemistry; D002417:Cattle; D002853:Chromatography, Liquid / Q000379:methods; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis*; D004285:Dogs; D004730:Endothelium, Vascular / Q000737:chemistry; D007668:Kidney / Q000737:chemistry; D008297:Male; D008861:Microsomes / Q000737:chemistry; D009206:Myocardium / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D012015:Reference Standards; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D016718:Arachidonic Acid; D003577:Cytochrome P-450 Enzyme System