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Characteristics and superoxide-induced activation of reconstituted myocardial mitochondrial ATP-sensitive potassium channels. Circ Res 2001 Dec 07;89(12):1177-83

Date

12/12/2001

Pubmed ID

11739283

DOI

10.1161/hh2401.101752

Scopus ID

2-s2.0-0035824922   170 Citations

Abstract

Mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels have been suggested as triggers and end effectors in myocardial ischemic preconditioning. However, the intracellular mechanism regulating mitoK(ATP) channels remains unclear. In the present study, mitoK(ATP) channels from bovine ventricular myocardium were reconstituted using planar lipid bilayers, and the effect of superoxide (O(2-.)) on the activity of these reconstituted channels was examined. After incorporation, a potassium-selective current was recorded. The mean conductance of this current was 56 pS at 150 mmol/L KCl, which was substantially inhibited by 1 mmol/L MgATP. 5-Hydroxydecanoate (5-HD, 10 to 100 micromol/L), a selective mitoK(ATP) antagonist, reduced the open state probability (NPo) of these channels in a concentration-dependent manner, whereas diazoxide (10 micromol/L), a selective mitoK(ATP) agonist, significantly increased channel activity. HMR-1098 (100 micromol/L), a selective sarcolemmal K(ATP) antagonist, had no effect on the activity of reconstituted channels. Addition of xanthine/xanthine oxidase (100 micromol/L per 0.038 U/mL), an O(2-.)-generating system, resulted in a marked activation of mitoK(ATP) channels; the NPo of the channels was increased from 0.60+/-0.10 to 1.94+/-0.02. This O(2)(-.)-induced channel activation was completely abolished by pretreatment with 5-HD (100 micromol/L) or a sulfhydryl alkylating compound, N-ethylmaleimide (2 mmol/L). It is concluded that myocardial mitoK(ATP) channels can be reconstituted into lipid bilayers and that O(2-.) activates these channels. The effect of O(2-.) may be associated with its direct action on the sulfhydryl groups of the channel protein.

Author List

Zhang DX, Chen YF, Campbell WB, Zou AP, Gross GJ, Li PL

Authors

William B. Campbell PhD Chair, Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin
David X. Zhang MD, PhD Associate Professor in the Medicine department at Medical College of Wisconsin




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

Adenosine Triphosphate
Animals
Benzamides
Cattle
Decanoic Acids
Diazoxide
Dose-Response Relationship, Drug
Ethylmaleimide
Glyburide
Guanosine Triphosphate
Hydroxy Acids
Ion Channel Gating
Lipid Bilayers
Membrane Potentials
Mitochondria, Heart
Myocardium
Potassium
Potassium Channels
Subcellular Fractions
Sulfhydryl Reagents
Superoxides
Xanthine
Xanthine Oxidase
jenkins-FCD Prod-482 91ad8a360b6da540234915ea01ff80e38bfdb40a