Pfister S L, Falck J R, Campbell W B
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235.
Am J Physiol. 1991 Sep;261(3 Pt 2):H843-52. doi: 10.1152/ajpheart.1991.261.3.H843.
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.
在从喂食标准兔粮或含2%胆固醇兔粮的兔子获取的胸主动脉组织中，研究了通过环氧化酶、脂氧合酶和细胞色素P-450环氧合酶的花生四烯酸代谢。将主动脉条与[14C]花生四烯酸和A23187一起孵育。从提取的培养基中得到的代谢产物通过高压液相色谱（HPLC）进行分离。正常和喂食胆固醇的兔主动脉合成前列腺素（PGs）和羟基二十碳四烯酸（HETEs）。主要的环氧化酶产物是6-酮-PGF1α和PGE2。与正常兔子相比，喂食胆固醇的兔子主动脉中基础6-酮-PGF1α的产生略有减少。12(S)-和15(S)-HETE是正常和喂食胆固醇的兔子主动脉中主要的脂氧合酶产物。其结构通过气相色谱-质谱联用（GC-MS）得以确认。只有喂食胆固醇的兔主动脉通过细胞色素P-450环氧合酶将花生四烯酸代谢为环氧二十碳三烯酸（EETs）。基于在HPLC上与已知的14C标记标准品共迁移以及典型质谱，鉴定出了14,15-、11,12-、8,9-和5,6-EET。用14,15-EET孵育正常主动脉会降低6-酮-PGF1α的基础合成。其他EETs则无此作用。这四种EET区域异构体使去甲肾上腺素预收缩的正常和喂食胆固醇的兔主动脉舒张。喂食胆固醇的兔子主动脉对14,15-EET的舒张反应更大。这些研究表明，在动脉粥样硬化发展之前，高胆固醇血症会通过环氧化酶和环氧合酶途径改变花生四烯酸代谢。
