Nifedipine reduces adenine nucleotide breakdown in ischemic rat heart

An ATP-sparing effect has been demonstrated for a number of calcium antagonists. Nifedipine probably has a similar action, but data supporting this view are limited. Therefore we decided to study the effect of nifedipine on high-energy phosphate (and carbohydrate) metabolism in the ischemic rat heart. Langendorff preparations were made ischemic for less than 15 min. The reduction in coronary flow was 60 or 70%. Apex displacement during ischemia, a measure of contractility, was comparable for nifedipine-treated and untreated hearts. Ischemia caused a considerable release of the AMP catabolites adenosine, inosine and (hypo)xanthine, and of lactate. Nifedipine (10-100 micrograms/l) prevented this in a dose-dependent way. The highest dose reduced the release of purines and lactate by 90% (P less than 0.01) and 60% (P less than 0.001), respectively. The drug acted in a similar way during reperfusion. Due to ischemia, the adenylate energy charge (ATP + 0.5 ADP)/(ATP + ADP + AMP), decreased 15% (P less than 0.001); nifedipine at a concentration of 100 micrograms/l prevented this decrease (P less than 0.05). We conclude that nifedipine exerts a beneficial effect on myocardial adenine nucleotide metabolism during ischemia and reperfusion.