Role of oxygen-derived free radicals in myocardial edema and ischemia in coronary microvascular embolization.

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Abstract
BACKGROUND Oxygen-derived free radicals are thought to injure the ischemic heart during coronary microvascular embolization. METHODS AND RESULTS To test this idea, microspheres (15 microns in diameter) were repetitively administered into the left anterior descending coronary artery to cause microvascular embolization in dogs. Myocardial contractile and metabolic dysfunctions were significantly attenuated after treatments with recombinant human superoxide dismutase, an acyl derivative of ascorbic acid (CV3611, 2-O-octadecylascorbic acid), and xanthine oxidase inhibitor (allopurinol). The free radical scavengers and inhibitor enhanced the coronary hyperemic flow response during embolization, and the total number of microspheres causing maximal embolization was increased by these drugs. When 8-phenyltheophylline was additionally administered with superoxide dismutase, these beneficial effects were abolished, indicating that coronary effects of these drugs may be due to increased release of adenosine during coronary microvascular embolization. CONCLUSIONS We conclude that oxygen radicals worsen the ischemic injury in coronary microembolization.