Polyphenol (-)-Epigallocatechin Gallate during Ischemia Limits Infarct Size Via Mitochondrial KATP Channel Activation in Isolated Rat Hearts

Polyphenol (-)-epigallocatechin gallate (EGCG), the most abundant catechin of green tea, appears to attenuate myocardial ischemia/reperfusion injury. We investigated the involvement of ATP-sensitive potassium (K-ATP) channels in EGCG-induced cardioprotection. Isolated rat hearts were subjected to 30 min of regional ischemia and 2 hr of reperfusion. EGCG was perfused for 40 min, from 10 min before to the end of index ischemia. A nonselective K-ATP channel blocker glibenclamide (GLI) and a selective mitochondrial K-ATP (mK(ATP)) channel blocker 5-hydroxydecanoate (HD) were perfused in EGCG-treated hearts. There were no differences in coronary flow and cardiodynamics including heart rate, left ventricular developed pressure, rate-pressure product, +dP/dt(max), and-dP/dt(min) throughout the experiments among groups. EGCG-treatment significantly reduced myocardial infarction (14.5 +/- 2.5% in EGCG 1 mu M and 4.0 +/- 1.7% in EGCG 10 mu M, P < 0.001 vs. control 27.2 +/- 1.4%). This anti-infarct effect was totally abrogated by 10 mu M GLI (24.6 +/- 1.5%, P < 0.001 vs. EGCG). Similarly, 100 mu M HD also aborted the anti-infarct effect of EGCG (24.1 +/- 1.2%, P < 0.001 vs. EGCG). These data support a role for the K-ATP channels in EGCG-induced cardioprotection. The mK(ATP) channels play a crucial role in the cardioprotection by EGCG.