Faculty Collaboration Database

Endothelium-independent, ouabain-sensitive relaxation of bovine coronary arteries by EETs. Am J Physiol Heart Circ Physiol 2001 Mar;280(3):H1113-21

Date

02/17/2001

Pubmed ID

11179054

DOI

10.1152/ajpheart.2001.280.3.H1113

Scopus ID

2-s2.0-0034975475 (requires institutional sign-in at Scopus site)   52 Citations

Abstract

Endothelium-derived hyperpolarizing factor (EDHF) is released in response to agonists such as ACh and bradykinin and regulates vascular smooth muscle tone. Several studies have indicated that ouabain blocks agonist-induced, endothelium-dependent hyperpolarization of smooth muscle. We have demonstrated that epoxyeicosatrienoic acids (EETs), cytochrome P-450 metabolites of arachidonic acid, function as EDHFs. To further test the hypothesis that EETs represent EDHFs, we have examined the effects of ouabain on the electrical and mechanical effects of 14,15- and 11,12-EET in bovine coronary arteries. These arteries are relaxed in a concentration-dependent manner to 14,15- and 11,12-EET (EC(50) = 6 x 10(-7) M), bradykinin (EC(50) = 1 x 10(-9) M), sodium nitroprusside (SNP; EC(50) = 2 x 10(-7) M), and bimakalim (BMK; EC(50) = 1 x 10(-7) M). 11,12-EET-induced relaxations were identical in vessels with and without an endothelium. Potassium chloride (1-15 x 10(-3) M) inhibited [(3)H]ouabain binding to smooth muscle cells but failed to relax the arteries. Ouabain (10(-5) to 10(-4) M) increased basal tone and inhibited the relaxations to bradykinin, 11,12-EET, and 14,15-EET, but not to SNP or BMK. Barium (3 x 10(-5) M) did not alter EET-induced relaxations and ouabain plus barium was similar to ouabain alone. Resting membrane potential (E(m)) of isolated smooth muscle cells was -50.2 +/- 0.5 mV. Ouabain (3 x 10(-5) and 1 x 10(-4) M) decreased E(m) (-48.4 +/- 0.2 mV), whereas 11,12-EET (10(-7) M) increased E(m) (-59.2 +/- 2.2 mV). Ouabain inhibited the 11,12-EET-induced increase in E(m). In cell-attached patch clamp studies, 11,12-EET significantly increased the open-state probability (NP(o)) of a calcium-activated potassium channel compared with control cells (0.26 +/- 0.06 vs. 0.02 +/- 0.01). Ouabain did not change NP(o) but blocked the 14,15-EET-induced increase in NP(o). These results indicate that: 1) EETs relax coronary arteries in an endothelium-independent manner, 2) unlike EETs, potassium chloride does not relax the coronary artery, and 3) ouabain inhibits bradykinin- and EET-induced relaxations as has been reported for EDHF. These findings provide further evidence that EETs are EDHFs.

Author List

Pratt PF, Li P, Hillard CJ, Kurian J, Campbell WB

Authors

William B. Campbell PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin
Cecilia J. Hillard PhD Associate Dean, Center Director, Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
8,11,14-Eicosatrienoic Acid
Animals
Benzopyrans
Biological Factors
Bradykinin
Cardiotonic Agents
Cattle
Coronary Vessels
Dihydropyridines
Electrophysiology
Endothelium, Vascular
Membrane Potentials
Muscle, Smooth, Vascular
Nitroprusside
Ouabain
Peptides
Potassium
Potassium Channels
Tritium
Vasoconstrictor Agents
Vasodilation
Vasodilator Agents