Identification of Epoxyeicosatrienoic Acids as Endothelium-Derived Hyperpolarizing Factors
- 1 March 1996
- journal article
- research article
- Published by Ovid Technologies (Wolters Kluwer Health) in Circulation Research
- Vol. 78 (3), 415-423
- https://doi.org/10.1161/01.res.78.3.415
Abstract
Endothelial cells release several compounds, including prostacyclin, NO, and endothelium-derived hyperpolarizing factor (EDHF), that mediate the vascular effects of vasoactive hormones. The identity of EDHF remains unknown. Since arachidonic acid causes endothelium-dependent relaxations of coronary arteries through its metabolism to epoxyeicosatrienoic acids (EETs) by cytochrome P450, we wondered if the EETs represent EDHFs. Precontracted bovine coronary arteries relaxed in an endothelium-dependent manner to methacholine. The cytochrome P450 inhibitors, SKF 525A and miconazole, significantly attenuated these relaxations. They were also inhibited by tetraethylammonium (TEA), an inhibitor of Ca2+-activated K+ channels, and by high [K+]o (20 mmol/L). Methacholine also caused hyperpolarization of coronary smooth muscle (−27±3.9 versus −40±5.1 mV), which was completely blocked by SKF 525A and miconazole. In vessels prelabeled with [3H]arachidonic acid, methacholine stimulated the release of 6-ketoprostaglandin F1α, 12-HETE, and the EETs. Arachidonic acid relaxed precontracted coronary arteries, which were also blocked by TEA, charybdotoxin, another Ca2+-activated K+ channel inhibitor, and high [K+]o. 14,15-EET, 11,12-EET, 8,9-EET, and 5,6-EET relaxed precontracted coronary vessels (EC50, 1×10−6 mol/L). The four regioisomers were equally active. TEA, charybdotoxin, and high [K+]o attenuated the EET relaxations. 11,12-EET hyperpolarized coronary smooth muscle cells from −37±0.2 to −59±0.3 mV. In the cell-attached mode of patch clamp, both 14,15-EET and 11,12-EET increased the open-state probability of a Ca2+-activated K+ channel in coronary smooth muscle cells. This effect was blocked by TEA and charybdotoxin. These data support the hypothesis that the EETs are EDHFs.Keywords
This publication has 21 references indexed in Scilit:
- Role of Cytochrome P-450 Enzymes and Metabolites of Arachidonic Acid in the Control of Vascular ToneJournal of Vascular Research, 1995
- Nonendothelial‐derived nitric oxide activates the ATP‐sensitive K+ channel of vascular smooth muscle cellsFEBS Letters, 1994
- Nitric oxide directly activates calcium-dependent potassium channels in vascular smooth muscleNature, 1994
- Arachidonic acid- and acetylcholine-induced relaxations of rabbit aorta.Hypertension, 1992
- Evidence that nitric oxide does not mediate the hyperpolarization and relaxation to acetylcholine in the rat small mesenteric arteryBritish Journal of Pharmacology, 1992
- Recent progress in potassium channel opener pharmacologyBiochemical Pharmacology, 1992
- Hyperpolarization and relaxation of arterial smooth muscle caused by nitric oxide derived from the endotheliumNature, 1990
- Endothelium-dependent effects of acetylcholine in rat aorta: a comparison with sodium nitroprusside and cromakalimBritish Journal of Pharmacology, 1988
- Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factorNature, 1987
- Presence of cytochrome P-450-dependent monooxygenase in intimal cells of the hog aorta.Hypertension, 1985