Flavone improves functional recovery after ischemia in isolated reperfused rabbit hearts

The effects of flavone (2-phenyl-1,4-benzopyrone), a modulator of the cytochrome P-450 monooxygenase system, on myocardial postischemic reperfusion recovery were examined in the present study. Left ventricular functional recovery was evaluated in isolated, crystalloid-perfused rabbit hearts after 2 hours of modestly hypothermic (34 degrees C) global ischemia. Four groups (n = 8 in each group) were studied and compared: a vehicle control group, a second group pretreated with flavone (8 x 10(-6) mol/L) before ischemia, a third group pretreated with flavone followed by SKF 525-A (1.7 x 10(-5) mol/L), an inhibitor of cytochrome P-450, and a fourth group pretreated with flavone followed by indomethacin (1 x 10(-6) mol/L), an inhibitor of cyclooxygenase. At 15, 30, and 45 minutes after reperfusion, recovery of left ventricular developed pressure in the control group averaged (mean +/- standard deviation) only 2.60% +/- 12.7%, 35.5% +/- 15.0%, and 42.9% +/- 13.5% of baseline, respectively. In the flavone-treated group, recovery was significantly better, averaging 67.7% +/- 10.7%, 73.9% +/- 9.3%, and 73.6% +/- 7.6% of baseline at the same time periods. Recovery of peak positive rate of pressure rise in the control group averaged 27.4% +/- 15.2%, 38.6% +/- 19.2%, and 45.4% +/- 18.6% of baseline at 15, 30, and 45 minutes of reperfusion, respectively. In the flavone-treated group recovery values were significantly higher, averaging 67.8% +/- 9.6%, 77.3% +/- 8.5%, and 77.0% +/- 9.0% of baseline. End-diastolic pressures were significantly lower in the flavone-treated group compared with the control group at all reperfusion time points. Myocardial oxygen consumption was significantly higher in the flavone-treated group at 30 and 45 minutes of reperfusion, as well. The improvement resulting from flavone infusion was abolished completely by SKF 525-A, providing support for the interpretation that the effects of flavone were mediated through the cytochrome P-450 system. The cyclooxygenase inhibitor indomethacin midly attenuated the effects of flavone pretreatment, suggesting that the effects of flavone were only minimally related to metabolites of cyclooxygenase. We conclude that pretreatment with flavone represents a promising approach to myocardial protection that may be due to modulation of the myocardial cytochrome P-450 system.