Effects of NKY-722, a novel calcium antagonist, on the changes of cardiac energy metabolism

Effects of NKY-722, a novel dihydropyridine-type calcium antagonist, on the reduction of the creatine phosphate (CP) in the rat heart during stimulation by drugs were studied using an in vivo ^^31 P-magnetic resonance spectrum (MRS). Sprague-Dawley male rats were anesthetized and MRS signals were obtained using a probe attached on the pleura. Dose-dependent significant reductions of CP were observed after isoproterenol (1 and 10 ug/ 100 g body weight) or vasopressin (27 and 270 ng/ 100 g body weight) injection. Signals for ATP did not change significantly after isoproterenol or vasopressin injection. Nicotine (60 ug/ 100 g body weight) also reduced CP. NKY-722 (3 ug/ 100 g body weight) itself showed no significant changes, however, it inhibited the reduction of CP by isoproterenol or vasopressin. These results indicated that the reductions of CP of myocardium by drug stimulations were detected in vivo by MRS system. A protective effect of NKY-722 for the reduction of myocardium energy metabolism was suggested.