Abstract: To assess the myocardial effects of verapamil (Ver) pre-treatment against is-chemia-reperfusion injury, ³¹P NMR was used to sequentially follow the time courses of high energy phosphates (HEP) contents and intracellular pH(pH_i) of the rat myocardium before, during and after total ischemia. After 30min of equilibration, the perfustion of isolated hearts was stopped for 30min and subsequent reperfusion lasted for 30min at 37℃.Ver (0.2μmol·L^-1) was added to the perfusate throughout the experiment. Ver induced a more complete restoration of coronary flow following reperfusion. ³¹P NMR determination suggested metabolically beneficial effects induced by Ver administration. Phosphocreatine (PCr) became undetectable after 10min of ischemia in control hearts, but remained at 20%of its preischemic levels in Ver group. Adenosine triphosphate (ATP) decreased more slowly in treated than in untreated hearts during ischemia, with the end-ischemic levels of ATP were 53% and 34% respectively. Myocardial ATP was not replenished afer reperfusion in both groups, but Ver induced a significant (P < 0.05) higher recovery of PCr on reflow.PCr/P_i (inorganic phosphate) ratios were very significantly (P < 0.01) higher for treated hearts than for control hearts during both the first 10min of ischemia and the reperfusion stage. Ver was also found to significantly attenuate the acidosis during ischemia and prevent the appearance of very acidic areas of the myocardium after reperfusion.

Key words: Verapamil, ³¹P NMR, Ischemia, Myocardial reperfusion injury, Energy metabolism