Mitochondrial KATP channel inhibition blunts arrhythmia protection in ischemic exercised hearts

Quindry JC, Schreiber L, Hosick P, Wrieden J, Irwin JM, Hoyt E. Mitochondrial K-ATP channel inhibition blunts arrhythmia protection in ischemic exercised hearts. Am J Physiol Heart Circ Physiol 299: H175-H183, 2010. First published April 30, 2010; doi:10.1152/ajpheart.01211.2009.-The mechanisms responsible for anti-arrhythmic protection during ischemia-reperfusion (IR) in exercised hearts are not fully understood. The purpose of this investigation was to examine whether the ATP-sensitive potassium channels in the mitochondria (mito K-ATP) and sarcolemma (sarc K-ATP) provide anti-arrhythmic protection in exercised hearts during IR. Male Sprague-Dawley rats were randomly assigned to cardioprotective treadmill exercise or sedentary conditions before IR (I = 20 min, R = 30 min) in vivo. Subsets of exercised animals received pharmacological inhibitors for mito K-ATP (5-hydroxydecanoate) or sarc K-ATP (HMR1098) before IR. Blinded analysis of digital ECG tracings revealed that mito K-ATP inhibition blunted the anti-arrhythmic effects of exercise, while sarc K-ATP inhibition did not. Endogenous antioxidant enzyme activities for total, CuZn, and Mn superoxide dismutase, catalase, and glutathione peroxidase from ischemic and perfused ventricular tissue were not mitigated by IR, although oxidative stress was elevated in sedentary and mito K-ATP-inhibited hearts from exercised animals. These findings suggest that the mito K-ATP channel provides anti-arrhythmic protection as part of exercise-mediated cardioprotection against IR. Furthermore, these data suggest that the observed anti-arrhythmic protection may be associated with preservation of redox balance in exercised hearts.