ESTROGEN DIMINISHES POSTISCHEMIC HYDROXYL RADICAL PRODUCTION

Reperfusion of blood flow to an ischemic myocardium is imperative to s urvival; ironically, it may also manifest several pathophysiological c onditions. The most important of these are reperfusion arrhythmias and tissue injury and/or death. The mechanisms involved in reperfusion ar rhythmias remain to be fully elucidated; however, increasing evidence indicates that reperfusion-induced arrhythmias are a free radical-medi ated phenomenon. Acute administration of conjugated equine estrogen to dogs attenuates ischemia-and reperfusion-induced arrhythmias. The car dioprotective effect of estrogens in postmenopausal women is well docu mented, and recent studies suggest that estrogens possess strong antio xidant properties, with equine estrogens most potent. In this study we show that administration of conjugated equine estrogen to fully anest hetized dogs abolishes the burst of OH radicals typically produced on reperfusion of the myocardium. This indicates that estrogen might atte nuate reperfusion-induced ventricular arrhythmias by virtue of its ant ioxidant properties, suggesting a novel cardioprotective effect of the hormone.