ATP-dependent potassium channels and mitochondrial permeability transition pores play roles in the cardioprotection of theaflavin in young rat

Previous studies have confirmed that tea polyphenols possess a broad spectrum of biological functions such as anti-oxidative, anti-bacterial, anti-tumor, anti-inflammatory, anti-viral and cardiovascular protection activities, as well as anti-cerebral ischemia-reperfusion injury properties. But the effect of tea polyphenols on ischemia/reperfusion heart has not been well elucidated. The aim of this study was to investigate the protective effect of theaflavin (TF1) and its underlying mechanism. Young male Sprague-Dawley (SD) rats were randomly divided into five groups: (1) the control group; (2) TF1 group; (3) glibenclamide + TF1 group; (4) 5-hydroxydecanoate (5-HD) + TF1 group; and (5) atractyloside + TF1 group. The Langendorff technique was used to record cardiac function in isolated rat heart before and after 30 min of global ischemia followed by 60 min of reperfusion. The parameters of cardiac function, including left ventricular developing pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), maximal differentials of LVDP (+/- LVdP/dt (max)) and coronary flow (CF), were measured. The results showed: (1) compared with the control group, TF1 (10, 20, 40 mu mol/l) displayed a better recovery of cardiac function after ischemia/reperfusion in a concentration-dependent manner. At 60 min of reperfusion, LVDP, +/- LVdP/dt (max) and CF in the TF1 group were much higher than those in the control group, whereas left ventricular end-diastolic pressure (LVEDP) in the TF1 group was lower than that in the control group (P < 0.01). (2) Pretreatment with glibenclamide (10 mu mol/l), a K-ATP antagonist, completely abolished the cardioprotective effects of TF1 (20 mu mol/l). Also, most of the effects of TF1 (20 mu mol/l) on cardiac function after 60 min of reperfusion were reversed by 5-HD (100 mu mol/l), a selective mitochondria K-ATP antagonist. (3) Atractyloside (20 mu mol/l), a mitochondrial permeability transition pore (mPTP) opener, administered at the beginning of 15 min of reperfusion completely abolished the cardioprotection of TF1 (20 mu mol/l). The results indicate that TF1 protects the rat heart against ischemia/reperfusion injury through the opening of K-ATP channels, particularly on the mitochondrial membrane, and inhibits mPTP opening.