We investigated the effects of metformin on myocardial metabolism during ischemia by effect of the presence or absence of NO on the cardioprotective effect of metformin in myocardial ischemic injury has not been clearly assessed. The purpose of the present study was to test the hypothesis that metformin contributes to the cardioprotective effect in the ischemic heart by actingin conjunction with NO, and that this contribution of NO to the metformin-induced cardioprotection is more pronounced during ischemia than during pre-ischemia. We assessed the effects of metformin by measuring myocardial energy metabolism using 31 P-nuclear magnetic resonance (NMR) spectroscopy in isolated rabbit hearts.

We investigated the effect of a novel cardioprotective agent, JTV-519, with or without a nitric oxide synthase inhibitor, L-NAME, on the myocardial metabolism and contraction during ischemia and reperfusion by means of phosphorus 31-nuclear magnetic resonance ( lated compounds during the ischemic period, could be blamed. Nonetheless, even in cases in which ATP does not decrease and creatine phosphate recovers rapidly after short periods of ischemia, stunning is already present. The fact that the stunned myocardium can respond well to inotropic stimulation by the dopamine, isoproterenol, calcium infusion, epinephrine, or postextrasystolic potentiation suggests that stunning represents a lack of available intracellular calcium, a failure of uptake of calcium by the sarcoplasmic reticulum, or a failure of the contractile proteins to respond to normal calcium concentration (2). Kusuoka et al. (3,4)

Although 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors can protect the myocardium against ischemic injury, the mechanisms of their effect have not yet been characterized at the cellular level. Therefore, we investigated the role of cardiac ATP-sensitive K+ (K(ATP)) channels induced by the HMG-CoA reductase inhibitor known as pravastatin on the myocardial metabolism during ischemia by phosphorus 31-nuclear magnetic resonance (31P-NMR) in isolated rabbit hearts. Forty-five min of continuous normothermic global ischemia was carried out. Pravastatin with or without the K(ATP) channel blocker glibenclamide or the nitric oxide synthase inhibitor L-NAME was administered beginning 60 min prior to the global ischemia. Twenty-eight hearts were divided into 4 experimental groups consisting of 7 hearts each: the control group, the P group consisting of pravastatin treatment, the P+G group consisting of pravastatin treatment with glibenclamide, and the P+L group consisting of pravastatin treatment with L-NAME. During ischemia, the decreases in adenosine triphosphate (ATP) and intracellular pH (pHi) were significantly inhibited in the P group in comparison with Control group (at end of ischemia, respectively; both p<0.01), as was the increase in inorganic phosphate (Pi) (at end of ischemia, p<0.01). However, the decreases in ATP and pHi and the increase in Pi were not inhibited in the P+G group during ischemia. The P+L group also showed no inhibition of the aforementioned parameters during the same period. These results suggest that pravastatin has a significant beneficial effect for improving the myocardial energy metabolism, which is provided by K(ATP) channels and nitric oxide (NO), during myocardial ischemia. The cardioprotection of HMG-CoA reductase inhibitor may be caused by the K(ATP) channels that are mediated by the NO.

The effect of a novel cardioprotective agent, JTV-519 on myocardial metabolism and contraction during ischemia and reperfusion was investigated by means of phosphorus 31-nuclear magnetic resonance (31P-NMR) in Langendorff rabbit hearts. Normothermic, 20-min, global ischemia was followed by 30-min of postischemic reperfusion and JTV-519 was administered from 40 min prior to the global ischemia. Adenosine triphosphate (ATP), creatine phosphate (PCr), inorganic phosphate (Pi), intracellular pH (pHi), left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP) and coronary flow were measured. Fourteen hearts were divided into 2 experimental groups of 7: Group I were controls and Group II were perfused with JTV-519 (10(-6) mol/L). During ischemia, Group II showed a significant (p<0.01) inhibition of the increase in Pi and LVEDP and the decrease in ATP and pHi, compared with Group I. After postischemic reperfusion, Group II also showed a significant (p<0.01) improvement in ATP and pHi as compared with Group I. There were no differences in LVDP or coronary flow during ischemia and reperfusion between the 2 groups. In conclusion, JTV-519 had a significant beneficial effect on myocardial energy metabolism and relaxation during both myocardial ischemia and reperfusion.

Although angiotensin converting enzyme (ACE) inhibitor and/or angiotensin II type 1 (AT1) receptor antagonist can protect the myocardium against ischemia-reperfusion injury, the mechanisms of the effect have not yet been characterized at the cellular level. We here examined the effect of the combination of an ACE inhibitor, temocaprilat, an AT1 receptor antagonist, CV-11974 and/or a nitric oxide synthase inhibitor, L-NAME, on the myocardial metabolism and contraction during ischemia and reperfusion by using phosphorus 31-nuclear magnetic resonance (31P-NMR) in Langendorff rabbit hearts. After normothermic 20 min global ischemia, postischemic reperfusion of 30 min was carried out. Twenty-one hearts were divided into three experimental groups consisting of 7 hearts each: a Tem+CV group perfused with a combination of temocaprilat and CV-11974; a Tem+CV+L-NAME group perfused with a combination of temocaprilat and CV-11974 plus L-NAME, and a control group. During ischemia, both the Tem+CV group and Tem+CV+L-NAME group showed a significant inhibition of the decrease in adenosine triphosphate (ATP) compared with the control group (p<0.01); the increase in ATP was 50+/-3%, 42+/-4%, and 19+/-4% in the Tem+CV group, Tem+CV+L-NAME group, and control group, respectively. Both experimental groups also showed a significant inhibition of the increase in left ventricular end-diastolic pressure (LVEDP) compared with the control group (p<0.01). After postischemic reperfusion, the Tem+CV group and Tem+CV+L-NAME group again showed a significant improvement of ATP as compared with the control group (p<0.01); the increase in ATP was 73+/-3%, 64+/-3%, and 47+/-4% in the Tem+CV group, Tem+CV+L-NAME group, and control group, respectively, and a significant decrease of LVEDP as compared with the control group (p<0.01). There were no differences in ATP, or LVEDP during ischemia and reperfusion between the Tem+CV group and Tem+CV+ L-NAME group. In conclusion, the combination of temocaprilat and CV-11974 showed significant potential for improving myocardial energy metabolism and relaxation during both myocardial ischemia and reperfusion. This beneficial effect was not dependent on NO synthase.