Cardioprotective effects of KRN2391 and nicorandil on ischemic dysfunction in perfused rat heart

The cardioprotective effect of KRN2391 (N-cyano-N-(2-nitroxymethyl)-3- pyridinecarboximidamide methanesulfonate), a novel vasodilator, was studied in the isolated perfused rat heart and compared with that of nicorandil. The isolated buffer-perfused rat heart was subjected to 25 min ischemia followed by 30 min reperfusion. The heart was pretreated with 0.1-10 microM KRN2391, 10-1000 microM nicorandil or vehicle. Before ischemia, KRN2391 (1-10 microM) and nicorandil (10-1000 microM) increased coronary flow, but did not modify the cardiac mechanical function. KRN2391 (1-10 microM) and nicorandil at high doses (300-1000 microM) resulted in significant improvements of cardiac functions and coronary flow during reperfusion and significantly reduced the release of cytosolic enzymes. The protective effects of 3 microM KRN2391 and 300 microM nicorandil were completely reversed by 3 microM glibenclamide, a blocker of ATP-sensitive potassium channels. Thus, KRN2391 and nicorandil at high doses have a direct cardioprotective effect, which may be related to activation of ATP-sensitive potassium channels.