Mechanism of rat mesenteric arterial KATP channel activation by 14,15-epoxyeicosatrienoic acid

Dan Ye, Wei Zhou, Tong Lu, Setti G. Jagadeesh, John R. Falck, Hon Chi Lee

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23 Scopus citations

Abstract

Recently, we reported that 11,12-epoxyeicosatrienoic acid (11,12-EET) potently activates rat mesenteric arterial ATP-sensitive K+ (K ATP) channels and produces significant vasodilation through protein kinase A-dependent mechanisms. In this study, we tried to further delineate the signaling steps involved in the activation of vascular KATP channels by EETs. Whole cell patch-clamp recordings [0.1 mM ATP in the pipette, holding potential (HP) = 0 mV and testing potential (TP) = -100 mV] in freshly isolated rat mesenteric smooth muscle cells showed small glibenclamide-sensitive K ATP currents (19.0 ± 7.9 pA, n = 5) that increased 6.9-fold on exposure to 5 μM 14,15-EET (132.0 ± 29.0 pA, n = 7, P < 0.05 vs. control). With 1 mM ATP in the pipette solution, KATP currents (HP = 0 mV and TP = -100 mV) were increased 3.5-fold on exposure to 1 μM 14,15-EET (57.5 ± 14.3 pA, n = 9, P < 0.05 vs. baseline). In the presence of 100 nM iberiotoxin, 1 μM 14,15-EET hyperpolarized the membrane potential from -20.5 ± 0.9 mV at baseline to -27.1 ± 3.0 mV (n = 6 for both, P < 0.05 vs. baseline), and the EET effects were significantly reversed by 10 μM glibenclamide (-21.8 ± 1.4 mV, n = 6, P < 0.05 vs. EET). Incubation with 5 μM 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE), a 14,15-EET antagonist, abolished the 14,15-EET effects (31.0 ± 11.8 pA, n = 5, P < 0.05 vs. 14,15-EET, P = not significant vs. control). The 14,15-EET effects were inhibited by inclusion of anti-Gsα antibody (1:500 dilution) but not by control IgG in the pipette solution. The effects of 14,15-EET were mimicked by cholera toxin (100 ng/ml), an exogenous ADP-ribosyltransferase. Treatment with the ADP-ribosyltransferase inhibitors 3-aminobenzamide (1 mM) or m-iodobenzylguanidine (100 μM) abrogated the effects of 14,15-EET on KATP currents. These results were corroborated by vasodilation studies. 14,15-EET dose-dependently dilated isolated small mesenteric arteries, and this was significantly attenuated by treatment with 14,15-EEZE or 3-aminobenzamide. These results suggest that 14,15-EET activates vascular KATP channels through ADP-ribosylation of Gsα.

Original languageEnglish (US)
Pages (from-to)H1326-H1336
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume290
Issue number4
DOIs
StatePublished - Apr 1 2006

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Keywords

  • ADP-ribosylation
  • ATP-sensitive potassium channel
  • Mesenteric artery

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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