Activation of ATP-sensitive K + channels by epoxyeicosatrienoic acids in rat cardiac ventricular myocytes

Tong Lu, Toshinori Hoshi, Neal L. Weintraub, Arthur A. Spector, Hon Chi Lee

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Abstract

1. We examined the effects of epoxyeicosatrienoic acids (EETs), which are cytochrome P450 metabolites of arachidonic acid (AA), on the activities of the ATP-sensitive K + (K ATP ) channels of rat cardiac myocytes, using the inside-out patch-clamp technique. 2. In the presence of 100 μM cytoplasmic ATP, the K ATP channel open probability (P o ) was increased by 240 ± 60% with 0.1 μM 11,12-EET and by 400 ± 54% with 5 μM 11,12-EET (n = 5-10, P < 0.05 vs. control), whereas neither 5 μM 11,12-dihydroxyeicosatrienoic acid (DHET), which is the epoxide hydrolysis product of 11,12-EET, had any effect on P o . 3. The half-maximal activating concentration (EC 50 ) was 18.9 ± 2.6 nM for 11,12-EET (n = 5) and 19.1 ± 4.8 nM for 8,9-EET (n = 5, P = n.s. vs. 11,12-EET). Furthermore, 11,12-EET failed to alter the inhibition of K ATP channels by glyburide. 4. Application of 11,12-EET markedly decreased the channel sensitivity to cytoplasmic ATP. The half-maximal inhibitory concentration of ATP (IC 50 ) was increased from 21.2 ± 2.0 μM at baseline to 240 ± 60 μM with 0.1 μM 11,12-EET (n = 5, P < 0.05 vs. control) and to 780 ± 30 μM with 5 μM 11,12-EET (n = 11, P < 0.05 vs. control). 5. Increasing the ATP concentration increased the number of kinetically distinguishable closed states, promoting prolonged closure durations. 11,12-EET antagonized the effects of ATP on the kinetics of the K ATP channels in a dose- and voltage-dependent manner. 11,12-EET (1 μM) reduced the apparent association rate constant of ATP to the channel by 135-fold. 6. Application of 5 μM 11,12-EET resulted in hyperpolarization of the resting membrane potential in isolated cardiac myocytes, which could be blocked by glyburide. 7. These results suggest that EETs are potent activators of the cardiac K ATP channels, modulating channel behaviour by reducing the channel sensitivity to ATP. Thus, EETs could be important endogenous regulators of cardiac electrical excitability.

Original languageEnglish (US)
Pages (from-to)811-827
Number of pages17
JournalJournal of Physiology
Volume537
Issue number3
DOIs
StatePublished - Dec 15 2001

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Cardiac Myocytes
Adenosine Triphosphate
Acids
Glyburide
11,12-epoxy-5,8,14-eicosatrienoic acid
Epoxy Compounds
Patch-Clamp Techniques
Arachidonic Acid
Membrane Potentials
Cytochrome P-450 Enzyme System
Hydrolysis

ASJC Scopus subject areas

  • Physiology

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Activation of ATP-sensitive K + channels by epoxyeicosatrienoic acids in rat cardiac ventricular myocytes . / Lu, Tong; Hoshi, Toshinori; Weintraub, Neal L.; Spector, Arthur A.; Lee, Hon Chi.

In: Journal of Physiology, Vol. 537, No. 3, 15.12.2001, p. 811-827.

Research output: Contribution to journalArticle

Lu, Tong ; Hoshi, Toshinori ; Weintraub, Neal L. ; Spector, Arthur A. ; Lee, Hon Chi. / Activation of ATP-sensitive K + channels by epoxyeicosatrienoic acids in rat cardiac ventricular myocytes In: Journal of Physiology. 2001 ; Vol. 537, No. 3. pp. 811-827.
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AU - Lee, Hon Chi

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N2 - 1. We examined the effects of epoxyeicosatrienoic acids (EETs), which are cytochrome P450 metabolites of arachidonic acid (AA), on the activities of the ATP-sensitive K + (K ATP ) channels of rat cardiac myocytes, using the inside-out patch-clamp technique. 2. In the presence of 100 μM cytoplasmic ATP, the K ATP channel open probability (P o ) was increased by 240 ± 60% with 0.1 μM 11,12-EET and by 400 ± 54% with 5 μM 11,12-EET (n = 5-10, P < 0.05 vs. control), whereas neither 5 μM 11,12-dihydroxyeicosatrienoic acid (DHET), which is the epoxide hydrolysis product of 11,12-EET, had any effect on P o . 3. The half-maximal activating concentration (EC 50 ) was 18.9 ± 2.6 nM for 11,12-EET (n = 5) and 19.1 ± 4.8 nM for 8,9-EET (n = 5, P = n.s. vs. 11,12-EET). Furthermore, 11,12-EET failed to alter the inhibition of K ATP channels by glyburide. 4. Application of 11,12-EET markedly decreased the channel sensitivity to cytoplasmic ATP. The half-maximal inhibitory concentration of ATP (IC 50 ) was increased from 21.2 ± 2.0 μM at baseline to 240 ± 60 μM with 0.1 μM 11,12-EET (n = 5, P < 0.05 vs. control) and to 780 ± 30 μM with 5 μM 11,12-EET (n = 11, P < 0.05 vs. control). 5. Increasing the ATP concentration increased the number of kinetically distinguishable closed states, promoting prolonged closure durations. 11,12-EET antagonized the effects of ATP on the kinetics of the K ATP channels in a dose- and voltage-dependent manner. 11,12-EET (1 μM) reduced the apparent association rate constant of ATP to the channel by 135-fold. 6. Application of 5 μM 11,12-EET resulted in hyperpolarization of the resting membrane potential in isolated cardiac myocytes, which could be blocked by glyburide. 7. These results suggest that EETs are potent activators of the cardiac K ATP channels, modulating channel behaviour by reducing the channel sensitivity to ATP. Thus, EETs could be important endogenous regulators of cardiac electrical excitability.

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