Protection of the myocardium against postischemic reperfusion damage. The combined effect of hypothermia and nifedipine.

This study tests the hypothesis that the efficacy of hypothermia as a cardiacprotective agent can be increased by adding the slow channel--blocking agent, nifedipine. Isolated, electrically paced rabbit hearts were made ischemic for 60 to 180 minutes at 37 degrees, 34 degrees, 28 degrees, 25 degrees, 15 degrees, 12 degrees, and 5 degrees C and then reperfused at 37 degrees C. Recovery was assessed in terms of recovery of mechanical function, tissue stores of adenosine triphosphate (ATP), oxidative phosphorylative and ATP-generating capacity of the mitochondria, and mitochondrial Ca2+ content. Half of the hearts received 50 micrograms/L nifedipine. The results show that the protective effects of hypothermia and nifedipine are additive.