Effects of diltiazem on high-energy phosphate contents reduced by isoproterenol in rat myocardium.

Effects of diltiazem on myocardial high-energy phosphate metabolism as well as on arterial blood pressure and heart rate were investigated in the rat treated with isoproterenol. Pretreatment with diltiazem prevented the reduction in both adenosine triphosphate and creatine phosphate induced by 2.5 mg/kg of isoproterenol. The ratio of creatine phosphate/inorganic phosphate in the rat receiving 100 mg/kg of diltiazem was higher than in the control. Heart rate was significantly decreased by the administration of 100 mg/kg of diltiazem not only in the non-pretreated rat but also in the rat given isoproterenol. This may partly account for the protective effect of diltiazem against the breakdown of high-energy phosphate in the isoproterenol-treated rat.