Ultrastructural damages in rat myocardium induced by hydrogen peroxide injection

Rat myocardium was examined by electron microscopy after hydrogen peroxide injection through the tail vein. At the initial stage (1-6 hr after injection of hydrogen peroxide), ultrastructural damages included slight edema of the myocytes, dilation of the sarcoplasmic reticulum, disruption of the myofibrils, interstitial edema and the disappearance of elastin. At the early stage (1-7 days), in addition to the ultrastructural damages of the myocardium in the initial stages, swelling and fusion of mitochondria, irregularly-arranged collagen networks and type III bleb formations were observed. At the later stage (14-28 days), tissue damages had recovered. There was little ultrastructural damage in the normal control myocardium. The relationship between oxygen-derived free radicals and early ischemic or ischemia-reperfusion injury is discussed.