Protection against ischemia-induced ventricular arrhythmias and myocardial dysfunction conferred by preconditioning in the rat heart: involvement of mitochondrial K(ATP) channels and reactive oxygen species.
Ischemic preconditioning (I-PC) induced by brief episodes of ischemia and reperfusion (I/R) protects the heart against sustained I/R. Although activation of mitochondrial K(ATP) channels (mitoK(ATP)) interacting with reactive oxygen species (ROS) has been proposed as a key event in this process, their role in the antiarrhythmic effect is not clear. This study was designed: 1) to investigate the involvement of mito K(ATP) opening in the effect of I-PC (1 cycle of I/R, 5 min each) on ventricular arrhythmias during test ischemia (TI, 30-min LAD coronary artery occlusion) in Langendorff-perfused rat hearts and subsequent postischemic contractile dysfunction, and 2) to characterize potential mechanisms of protection conferred by I-PC and pharmacological PC induced by mito K(ATP) opener diazoxide (DZX), with particular regards to the modulation of ROS generation. Lipid peroxidation (an indicator of increased ROS production) was determined by measurement of myocardial concentration of conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) in non-ischemic controls, non-preconditioned and preconditioned hearts exposed to TI, I-PC alone, as well as after pretreatment with DZX, mito K(ATP) blocker 5-hydroxydecanoate (5-HD) and antioxidant N-acetylcysteine (NAC). Total number of ventricular premature beats (VPB) that occurred in the control hearts (518+/-71) was significantly (P<0.05) reduced by I-PC (195+/-40), NAC (290+/-56) and DZX (168+/-22). I-PC and NAC suppressed an increase in CD and TBARS caused by ischemia indicating lower production of ROS. On the other hand, I-PC and DZX themselves moderately enhanced ROS generation, prior to TI. Bracketing of I-PC with 5-HD suppressed both, ROS production during PC and its cardioprotective effect. In conclusion, potential mechanisms of protection conferred by mito K(ATP) opening in the rat heart might involve a temporal increase in ROS production in the preconditioning phase triggering changes in the pro/antioxidant balance in the myocardium and attenuating ROS production during subsequent prolonged ischemia.
Matejíková
J
J
Institute for Heart Research, Slovak Academy of Sciences, Bratislava, Slovak Republic.
Kucharská
J
J
Pintérová
M
M
Pancza
D
D
Ravingerová
T
T
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D003652:Decanoic Acids / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D006880:Hydroxy Acids / Q000494:pharmacology; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D015227:Lipid Peroxidation; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism*; D018384:Oxidative Stress; D010477:Perfusion; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020127:Recovery of Function; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D013997:Time Factors; D016277:Ventricular Function, Left / Q000187:drug effects; D018879:Ventricular Premature Complexes / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*
D000889:Anti-Arrhythmia Agents; D000975:Antioxidants; D003652:Decanoic Acids; D006880:Hydroxy Acids; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D017382:Reactive Oxygen Species; D017392:Thiobarbituric Acid Reactive Substances; C117780:mitochondrial K(ATP) channel; C052853:5-hydroxydecanoic acid; D003981:Diazoxide; D000111:Acetylcysteine