Enhanced synthesis of epoxyeicosatrienoic acids by cholesterol-fed rabbit aorta.
Arachidonic acid metabolism via cyclooxygenase, lipoxygenase, and cytochrome P-450 epoxygenase was investigated in thoracic aortic tissue obtained from rabbits fed either standard rabbit chow or chow containing 2% cholesterol. Aortic strips were incubated with [14C]arachidonic acid and A23187. Metabolites from extracted media were resolved by high-pressure liquid chromatography (HPLC). Normal and cholesterol-fed rabbit aortas synthesized prostaglandins (PGs) and hydroxyeicosatetraenoic acids (HETEs). The major cyclooxygenase products were 6-keto-PGF1 alpha and PGE2. Basal aortic 6-keto-PGF1 alpha production was slightly reduced in cholesterol-fed compared with normal rabbits. 12(S)- and 15(S)-HETE were the major aortic lipoxygenase products from both normal and cholesterol-fed rabbits. The structures were confirmed by gas chromatography-mass spectrometry (GC-MS). Only cholesterol-fed rabbit aortas metabolized arachidonic acid via cytochrome P-450 epoxygenase to the epoxyeicosatrienoic acids (EETs). 14,15-, 11,12-, 8,9-, and 5,6-EET were identified based on comigration on HPLC with known 14C-labeled standards and typical mass spectra. Incubation of normal aorta with 14,15-EET decreased the basal synthesis of 6-keto-PGF1 alpha. The other EETs were without effect. The four EET regioisomers relaxed the norepinephrine-precontracted normal and cholesterol-fed rabbit aorta. The relaxation response to 14,15-EET was greater in aortas from cholesterol-fed rabbits. These studies demonstrate that hypercholesterolemia, before the development of atherosclerosis, alters arachidonic acid metabolism via both the cyclooxygenase and epoxygenase pathways.
Pfister
S L
SL
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235.
Falck
J R
JR
Campbell
W B
WB
D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D015772:4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine / Q000494:pharmacology; D015121:6-Ketoprostaglandin F1 alpha / Q000378:metabolism; D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism*; D001095:Arachidonic Acids / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002791:Cholesterol, Dietary / Q000494:pharmacology*; D003022:Clotrimazole / Q000494:pharmacology; D004036:Diet, Atherogenic; D006893:Hydroxyeicosatetraenoic Acids / Q000302:isolation & purification / Q000378:metabolism*; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007700:Kinetics; D009637:Masoprocol / Q000494:pharmacology; D008797:Metyrapone / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D011817:Rabbits; D012016:Reference Values; D013237:Stereoisomerism
D001095:Arachidonic Acids; D002250:Carbon Radioisotopes; D002791:Cholesterol, Dietary; D006893:Hydroxyeicosatetraenoic Acids; D015121:6-Ketoprostaglandin F1 alpha; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; C046783:11,12-epoxy-5,8,14-eicosatrienoic acid; D015772:4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; C027356:11-hydroxy-5,8,12,14-eicosatetraenoic acid; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; D009637:Masoprocol; C040776:5,6-epoxy-8,11,14-eicosatrienoic acid; C050715:8,9-epoxyeicosatrienoic acid; C046782:14,15-epoxy-5,8,11-eicosatrienoic acid; D015126:8,11,14-Eicosatrienoic Acid; D003022:Clotrimazole; D007213:Indomethacin; D008797:Metyrapone