A possible involvement of oxygen free radicals in the development of myocardial acidosis during coronary occlusion in dogs.

The present study was designed to examine whether free radical scavengers attenuate myocardial acidosis induced by partial occlusion of the coronary artery in dogs. The myocardial pH was determined by a micro glass pH electrode inserted in the endocardial layers of the left ventricular wall perfused by the left anterior descending coronary artery. The left anterior descending coronary artery was occluded for 90 min incompletely so that the flow would be 1/2-1/3 the original flow. The myocardial pH before partial occlusion was 7.54-7.55. Partial occlusion decreased the flow in the left anterior descending coronary artery by 49.3-64.9% and the myocardial pH by 0.71-0.76, and increased the ST segment (surface electrocardiogram) by 6.3-9.3 mV. Saline (0.5 ml/kg), recombinant human superoxide dismutase (70,000 or 210,000 U/kg), or catalase (55,000 or 165,000 U/kg) was injected intravenously 30 min after partial occlusion. The injection of recombinant human superoxide dismutase or catalase alone did not restore the myocardial pH that had been decreased by coronary occlusion. The combined injection of recombinant human superoxide dismutase (70,000 U/kg) + catalase (55,000 U/kg), however, restored the myocardial pH without restoration of ST segment. In conclusion, recombinant human superoxide dismutase + catalase attenuated myocardial acidosis during ischaemia, suggesting a possible involvement of oxygen free radicals in the development of myocardial acidosis (especially in the endocardial layers) during ischaemia.