Protective effects of m-nifedipine and nifedipine on ischemic-reperfused injury in working guinea pig hearts

The effects of m-nifedipine (m-Nif) on global myocardial ischemia and reperfusion have been compared with those of nifedipine (Nif) in the isolated working guinea pig hearts. Stronger coronary vasodilatation and less prominent cardiac depression were observed in the nonischemic hearts treated with m-Nif (8 and 25 nmol/L) than in those treated with the same doses of Nif. Hearts treated with m-Nif or Nif before and during low-flow ischemia, which lasted 50 min followed by 35 min reperfusion, showed significant preservation of contractility and relaxation, especially relaxation. These treatments resulted in a greater recovery of coronary flow and cardiac output, improvement of left ventricular work and efficiency, a reduction in creatine kinase release, and attenuation of myocardial edema. The treatments (m-Nif 25 and Nif 8 nmol/L), which were equiactive in nonischemic hearts, provided equivalent myocardial protection in reperfused ischemic hearts.