Abstract
The effects of nitroglycerin, dipyridamole, papaverine and anoxia on the cellular redox state were investigated in the inner and outer layers of the left ventricular wall, in open-chest dogs anesthetized with morphine and pentobarbital. As an index of the cellular redox state, the NAD+/NADH ratio was employed. The NAD+/NADH ratio was calculated by direct measurements of NAD+ and NADH in the tissue. In the control dog, the NAD+/NADH ratio in the inner layers was usually lower than that in the outer; a transmural gradient of the NAD+/NADH ratio across the left ventricle was detected. Anoxia was produced by discontinuation of artificial respiration for 3 min. In the anoxic dog, the NAD+/NADH ratios in both the layers were markedly lower than those obtained in the control dog. The transmural gradient of the NAD+/NADH ratio was not modified by the injection of either dipyridamole (250 μ/kg, i.v.) or papaverine (2 mg/kg, i.v.), but it was increased by the production of anoxia, while it was abolished by the injection of nitroglycerin (20 μg/kg, i.v.). The possible mechanisms of the beneficial action of nitroglycerin against angina pectoris are discussed with special reference to the myocardial redox state.
