Activation of rat mesenteric arterial KATP channels by 11,12-epoxyeicosatrienoic acid.
Epoxyeicosatrienoic acids (EETs), the cytochrome P-450 epoxygenase metabolites of arachidonic acid, are candidates of endothelium-derived hyperpolarizing factors. We have previously reported that EETs are potent activators of cardiac ATP-sensitive K(+) (K(ATP)) channels, but their effects on the vascular K(ATP) channels are unknown. With the use of whole cell patch-clamp techniques with 0.1 mM ATP in the pipette and holding at -60 mV, freshly isolated smooth muscle cells from rat mesenteric arteries had small glibenclamide-sensitive currents at baseline (13.1 +/- 3.9 pA, n = 5) that showed a 7.2-fold activation by 10 microM pinacidil (94.1 +/- 21.9 pA, n = 7, P < 0.05). 11,12-EET dose dependently activated the K(ATP) current with an apparent EC(50) of 87 nM. Activation of the K(ATP) channels by 500 nM 11,12-EET was inhibited by inclusion of the PKA inhibitor peptide (5 microM) but not by the inclusion of the PKC inhibitor peptide (100 microM) in the pipette solution. These results were corroborated by vasoreactivity studies. 11,12-EET produced dose-dependent vasorelaxation in isolated small mesenteric arteries, and this effect was reduced by 50% with glibenclamide (1 microM) preincubation. The 11,12-EET effects on vasorelaxation were also significantly attenuated by preincubation with cell-permeant PKA inhibitor myristoylated PKI(14-22), and, in the presence of PKA inhibitor, glibenclamide had no additional effects. These results suggest that 11,12-EET is a potent activator of the vascular K(ATP) channels, and its effects are dependent on PKA activities.
Ye
Dan
D
Division of Cardiovascular Diseases, Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, USA.
Zhou
Wei
W
Lee
Hon-Chi
HC
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D066298:In Vitro Techniques; D008638:Mesenteric Arteries / Q000378:metabolism* / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D014664:Vasodilation / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology*
D015221:Potassium Channels; 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; D000255:Adenosine Triphosphate; D017868:Cyclic AMP-Dependent Protein Kinases; D015126:8,11,14-Eicosatrienoic Acid