Effects of MCI-176, a new quinazolinone calcium antagonist, on myocardial energy and carbohydrate metabolism in ischemic dog hearts

Effect of efonidipine, a novel dihydropyridine derivative, on myocardial metabolic changes induced by coronary artery ligation in dogs: comparison with nifedipine

Efonidipine is a dihydropyridine derivative having a vasodilating action, which is slower in onset and longer in duration than that of nifedipine. In the present study, we compared the effects of efonidipine with those of nifedipine on the ischemic myocardial metabolism in anesthetized dogs. The heart was made ischemic by ligating the left anterior descending coronary artery (LAD) completely for 3 or 30 min. Efonidipine or nifedipine was injected intravenously, 10 or 3 min, respectively, before the start of LAD occlusion. Efonidipine (0.01 or 0.03 mg/kg) decreased both blood pressure and heart rate, whereas nifedipine (0.003 mg/kg) decreased blood pressure and increased heart rate. The magnitude of decrease in mean blood pressure induced by 0.03 mg/kg efonidipine was similar to that induced by 0.003 mg/kg nifedipine. Although efonidipine did not modify the changes in myocardial carbohydrate metabolism induced by ischemia, it attenuated the ischemia-induced decrease in the myocardial level of adenosine triphosphate and energy charge potential. Nifedipine, however, did not modify the changes in both myocardial energy and carbohydrate metabolism induced by ischemia. The results suggest that efonidipine has a cardioprotective effect in the dog, probably because of its negative chronotropic effect.

Effects of LP-805, a newly developed vasodilator, on myocardial metabolism in ischaemic dog hearts

The effects of LP-805, a newly developed vasodilator, on changes in the myocardial energy and carbohydrate metabolism induced by ischaemia were studied in open-chest anaesthetized dogs. Ischaemia was induced by ligating the left anterior descending coronary artery for 3 min. The myocardial energy stores were depleted, and the levels of glycolytic intermediates were altered 3 min after the onset of ischaemia. Energy change potential was decreased, and ([G6P] + [F6P])/[FDP] and [lactate]/[pyruvate] ratios were increased by ischaemia. These findings indicated that the myocardial metabolism was converted from an aerobic to an anaerobic type by ischaemia. LP-805 (10, 30, or 100 micrograms kg-1) was injected intravenously 5 min before the onset of ischaemia. LP-805 prevented the myocardial energy depletion and alterations of myocardial carbohydrate metabolism due to ischaemia, indicating that it appeared to convert the anaerobic metabolism back to aerobic metabolism in the ischaemic myocardium. In conclusion, LP-805 may reduce the ischaemic influence on the myocardium.