Korean Circ J.  2016 Jul;46(4):562-568. 10.4070/kcj.2016.46.4.562.

Influence of Thromboxane Aâ‚‚ on the Regulation of Adenosine Triphosphate-Sensitive Potassium Channels in Mouse Ventricular Myocytes

• Jeong IS
• Cho HJ
• Cho JG
• Kim SH
• Na KJ
• Kim JK

• KMID: 2344433
• DOI: http://doi.org/10.4070/kcj.2016.46.4.562

Abstract

BACKGROUND AND OBJECTIVES
Adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels play an important role in myocardial protection. We examined the effects of thromboxane Aâ‚‚ on the regulation of K(ATP) channel activity in single ventricular myocytes.
SUBJECTS AND METHODS
Single ventricular myocytes were isolated from the hearts of adult Institute of Cancer Research (ICR) mice by enzymatic digestion. Single channel activity was recorded by excised inside-out and cell-attached patch clamp configurations at -60 mV holding potential during the perfusion of an ATP-free K-5 solution.
RESULTS
In the excised inside-out patches, the thromboxane Aâ‚‚ analog, U46619, decreased the K(ATP) channel activity in a dose-dependent manner; however, the thromboxane Aâ‚‚ receptor antagonist, SQ29548, did not significantly attenuate the inhibitory effect of U46619. In the cell-attached patches, U46619 inhibited dinitrophenol (DNP)-induced K(ATP) channel activity in a dose-dependent manner, and SQ29548 attenuated the inhibitory effects of U46619 on DNP-induced K(ATP) channel activity.
CONCLUSION
Thromboxane Aâ‚‚ may inhibit K(ATP) channel activity, and may have a harmful effect on ischemic myocardium.

Keyword

KATP channels; Thromboxane Aâ‚‚; Myocytes; Cardiac

MeSH Terms

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
Adenosine Triphosphate
Adenosine*
Adult
Animals
Digestion
Heart
Humans
KATP Channels
Mice*
Muscle Cells*
Myocardium
Perfusion
Potassium Channels*
Potassium*
15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
Adenosine
Adenosine Triphosphate
KATP Channels
Potassium
Potassium Channels

Figure

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  Fig. 1 Cell-attached (left) and excised inside-out (right) patch clamp configurations.

• 

  Fig. 2 Typical ATP-sensitive K+ (KATP) channel activity in an excised inside-out patch (HP=-60 mV). Channel activity appeared immediately after making an excised inside-out patch, and ATP (1 mM) almost completely inhibited the channel activity. Channel activity reappeared when the ATP was washed out with the bath solution, and the KATP channel inhibitor, glibenclamide (50 µM) inhibited the channel activity. ATP: adenosine triphosphate.

• 

  Fig. 3 Current-voltage relationships of the ATP-sensitive K+ (KATP) channel in the excised inside-out patch at different clamp potentials ranging from −100 to +100 mV (left panel). The current-voltage relationship (right panel) was plotted with the single channel currents in the left panel. HP: holding potential, ATP: adenosine triphosphate.

• 

  Fig. 4 Effects of thromboxane A2 analog, U46619 (range 1–10 µM) on KATP channel activity in the excised inside-out patch (HP=-60 mV). U46619 inhibited KATP channel activity in a dose dependent manner (upper trace). Both the opening frequencies and the mean open-burst durations were markedly decreased at the times marked (a) and (b) on the expanded scale, but single-channel current amplitudes were not affected (lower two traces).

• 

  Fig. 5 Influence of thromboxane A2 analog, U46619, on current-voltage, KATP channel relationships in the excised inside-out patch at different clamp potentials. U46619 did not significantly change the channel conductance. pA: pico ampere, CTRL: control.

• 

  Fig. 6 Influence of thromboxane A2 receptor antagonist, SQ29548 (0.1 µM), on the inhibitory effects of a thromboxane A2 analog, U46619 in an excised inside-out patch (HP=-60 mV). SQ29548 did not influence the inhibitory effects of U46619.

• 

  Fig. 7 Typical ATP-sensitive K+ (KATP) channel activity in a cell-attached patch (HP=-60 mV). The KATP channel inhibitor, glibenclamide, inhibited the DNP-induced channel activity. ATP: adenosine triphosphate, DNP: dinitrophenol.

• 

  Fig. 8 Effects of the thromboxane A2 analog, U46619 (1 and 10 µM), on the DNP-induced KATP channel activity in a cell-attached patch (HP=-60 mV). U46619 decreased the DNP-induced channel activity in a dose-dependent manner. DNP: dinitrophenol, ATP: adenosine triphosphate.

• 

  Fig. 9 Influence of the thromboxane A2 receptor antagonist, SQ29548 (0.1 µM), on DNP-induced KATP channel activity in a cell-attached patch (HP=−60 mV). SQ29548 attenuated the inhibitory effects of the thromboxane A2 analog, U46619, on DNP-induced KATP channel activity. DNP: dinitrophenol.

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