Glyburide, a K-ATP channel antagonist, attenuates the cardioprotective effects of isoflurane in stunned myocardium

This investigation examined the role of myocardial adenosine triphosphate-regulated potassium (K-ATP) channels in isoflurane-induced enhancement of myocardial function after reversible tissue injury produced by a 15-min left anterior descending coronary artery occlusion (LAD) and reperfusion. Dogs (n = 14) were chronically instrumented for measurement of left ventricular (LV) and aortic blood pressure, cardiac output, coronary blood flow velocity, and subendocardial segment length. Regional myocardial contractility was evaluated with preload recruitable work area (PRWA). Isovolumic relaxation was assessed with a time constant (tau). Hemodynamic variables and LV function were measured in the conscious state, during 2% isoflurane anesthesia for 45 min before and during a 15-min LAD occlusion, and at several intervals after reperfusion in dogs pretreated with glyburide (0.3 mg/kg, intravenously) or drug vehicle. LAD occlusion caused regional dyskinesia and increases in tau. Vehicle-pretreated dogs demonstrated full recovery of segment shortening by 5 h postreperfusion and recovery of PRWA and tau by 30 min postreperfusion. In contrast, dogs pretreated with glyburide demonstrated sustained systolic and diastolic dysfunction. Segment shortening recovered to only 70% +/- 5%, PRWA remained depressed at 48% +/- 10%, and tau was prolonged to 116% +/- 5% of control values at 5 h postreperfusion. The results indicate that isoflurane enhances recovery of myocardial contractile function by 5 h postreperfusion, in comparison to previous findings in conscious dogs. These effects are partially blocked by glyburide pretreatment, indicating that K-ATP channel activation by isoflurane may mediate these cardioprotective effects.