Identification of epoxyeicosatrienoic acids as endothelium-derived hyperpolarizing factors. Circ Res 1996 Mar;78(3):415-23
Date
03/01/1996Pubmed ID
8593700DOI
10.1161/01.res.78.3.415Scopus ID
2-s2.0-0030051805 (requires institutional sign-in at Scopus site) 1123 CitationsAbstract
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+]0 (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 F1alpha, 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+]0. 14,15-EET, 11,12-EET, 8,9-EET, and 5,6-EET relaxed precontracted coronary vessels (EC50, 1 X 10(-6) mol/L). The four regioisomers were equally active. TEA, charybdotoxin, and high [K+]0 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.
Author List
Campbell WB, Gebremedhin D, Pratt PF, Harder DRAuthor
William B. Campbell PhD Professor in the Pharmacology and Toxicology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
8,11,14-Eicosatrienoic AcidAnimals
Arachidonic Acid
Biological Factors
Cattle
Coronary Vessels
Cyclic AMP
Cyclic GMP
Cytochrome P-450 Enzyme Inhibitors
Endothelium, Vascular
In Vitro Techniques
Muscle Relaxation
Nitric Oxide
Patch-Clamp Techniques