Comparison of the protective effects of a highly selective ATP-sensitive potassium channel opener and ischemic preconditioning in isolated human atrial muscle

The ATP-sensitive K+ channel(K-ATP channel) has been implicated in the mechanism of ischemic preconditioning. We compared the protective effects of ischemic preconditioning and a highly selective K-ATP channel opener, BMS 180448, in human myocardium. BMS 180448 was either used alone or in combination with the K-ATP channel blocker glibenclamide. Human atrial trabeculae derived from the right atrial appendage were suspended in an organ bath, superfused with oxygenated Tyrode's solution at 37 degrees C, and paced at 1 Hz. Experimental groups (n = 6 in each) were as follows: (I)control(C)-90 minutes hypoxic substrate-free perfusion at 3 Hz (simulated ischemia), followed by 120 minutes of reoxygenation with substrate at 1 Hz (reperfusion); (2) preconditioning (PC)3 minutes simulated ischemia, 7 minutes reperfusion, followed by 90 minutes simulated ischemia, and 120 minutes reperfusion; (3)BMS 180448 (BMS)-exposure to the drug for 5 minutes prior to 90 minutes simulated ischemia and 120 minutes reperfusion; (4) BMS 180448+glibenclamide (BMS+G)-glibenclamide exposure for 10 minutes, and BMS for 5 minutes prior to 90 minutes simulated ischemia and 120 minutes reperfusion. Force of contraction prior to the commencement of the protocol was assigned the arbitrary value of 100%. Percentage recovery of contractile function at 120 minutes reperfusion was used as the endpoint. BMS (59.2 +/- 8.6%) and preconditioning (50.5 +/- 3.6%) produced a similar degree of recovery of function at the end of 120 minutes of reperfusion; this was significantly different from the untreated control group (20.8 +/- 3.59%, p < 0.05, ANOVA). When glibenclamide was added prior to BMS, protection was lost (20.5 +/- 2.7%). In this human atrial preparation, a highly selective K-ATP channel opener mimicked the protective effect of ischemic preconditioning. This protective effect of BMS was abolished by glibenclamide. These findings confirm that the mechanism of ischemic preconditioning in human muscle may be mediated via opening of the K-ATP channel.