Redox State of Nicotinamide-Adenine Dinucleotide in the Inner and Outer Layers of Canine Left Ventricle, and Effects of Coronary Dilators on the Redox State

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 cither dipyridamole (250 μg/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 arc discussed with special reference to the myocardial redox state.