8-9-epoxyeicosatrienoic-acid and 11-hydroxy-5-8-12-14-eicosatetraenoic-acid

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.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; 4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; 6-Ketoprostaglandin F1 alpha; 8,11,14-Eicosatrienoic Acid; Animals; Aorta, Thoracic; Arachidonic Acids; Carbon Radioisotopes; Cholesterol, Dietary; Clotrimazole; Diet, Atherogenic; Hydroxyeicosatetraenoic Acids; In Vitro Techniques; Indomethacin; Kinetics; Masoprocol; Metyrapone; Muscle, Smooth, Vascular; Rabbits; Reference Values; Stereoisomerism