title: Epoxyeicosatrienoic acids increase intracellular calcium concentration in vascular smooth muscle cells.
abstract: Epoxyeicosatrienoic acids (EETs) are cytochrome P450-derived metabolites of arachidonic acid. They are potent endogenous vasodilator compounds produced by vascular cells, and EET-induced vasodilation has been attributed to activation of vascular smooth muscle cell (SMC) K(+) channels. However, in some cells, EETs activate Ca(2+) channels, resulting in Ca(2+) influx and increased intracellular Ca(2+) concentration ([Ca(2+)](i)). We investigated whether EETs also can activate Ca(2+) channels in vascular SMC and whether the resultant Ca(2+) influx can influence vascular tone. The 4 EET regioisomers (1 micromol/L) increased porcine aortic SMC [Ca(2+)](i) by 52% to 81%, whereas arachidonic acid, dihydroxyeicosatrienoic acids, and 15-hydroxyeicosatetraenoic acid (1 micromol/L) produced little effect. The increases in [Ca(2+)](i) produced by 14,15-EET were abolished by removal of extracellular Ca(2+) and by pretreatment with verapamil (10 micromol/L), an inhibitor of voltage-dependent (L-type) Ca(2+) channels. 14,15-EET did not alter Ca(2+) signaling induced by norepinephrine and thapsigargin. When administered to porcine coronary artery rings precontracted with a thromboxane mimetic, 14,15-EET produced relaxation. However, when administered to rings precontracted with acetylcholine or KCl, 14,15-EET produced additional contractions. In rings exposed to 10 mmol/L KCl, a concentration that did not affect resting ring tension, 14,15-EET produced small contractions that were abolished by EGTA (3 mmol/L) or verapamil (10 micromol/L). These observations indicate that 14,15-EET enhances [Ca(2+)](i) influx in vascular SMC through voltage-dependent Ca(2+) channels. This 14,15-EET-induced increase in [Ca(i)(2+)] can produce vasoconstriction and therefore may act to modulate EET-induced vasorelaxation.
authors.affiliation: Department of Biochemistry, University of Iowa College of Medicine, Iowa City 52242, USA. xiang-fang@uiowa.edu
authors.forename: X
authors.initials: X
authors.lastname: Fang
authors.forename: N L
authors.initials: NL
authors.lastname: Weintraub
authors.forename: L L
authors.initials: LL
authors.lastname: Stoll
authors.forename: A A
authors.initials: AA
authors.lastname: Spector
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013552:Swine; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D002614:Chelating Agents; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; C046783:11,12-epoxy-5,8,14-eicosatrienoic acid; 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; D002118:Calcium