It was shown that ATP-sensitive potassium (K-ATP) channel openers protected the myocardium from the ischemia-reperfusion injury, however little is known about its influence on myocardium functions. We used the new fluoring-containing K-ATP channel openers (indicated as DiazoFm and PF-5) for the investigation their effect on the functions isolated rat hearts. We have shown that they did not significantly change the myocardial functions under physiological conditions but improved its recovery after the ischemia-reperfusion damage. Thus DiazoFm increased recovery of the left ventricular development pressure by 1,75 times in comparison to the control group, shorted time which needed for myocardial functions recovery after ischemia (by 2,29 times) and diminished the extrasystoles. Activators decresed the content of malonic dialdehyde (by 17%)and an area of chemoluminescence in ischemic myocardium. DiazoFm and PF-5 also regulated of the mitochondrial functions (oxidative phosphorylation and swelling). Consequently, DiazoFm and PF-5 improvement of functions iscemic myocardium and its cardioprotective mechanism related with both mitochondrial and sarcolemal K-ATP channel activation, diminution the generation of reactive oxygen species and regulation of mitochondrial functions.