We investigated the effects of estrogen on global myocardial ischemia-reperfusion injury in rats that were ovariectomized (Ovx), sham-operated, or ovariectomized and then given 17β-estradiol (E2β) supplementation (Ovx+E2β). Hearts were excised, cannulated, perfused with and then immersed in chilled (4°C) cardioplegia solution for 30 min, and then retrogradely perfused with warm (37°C), oxygenated Krebs-Henseleit bicarbonate buffer for 120 min. The coronary flow rate, first derivative of left ventricular pressure, and nitrite production were all significantly lower in Ovx than in sham-operated or Ovx+E2β hearts. However, coronary flow rates or nitrate production were not consistently different throughout the entire reperfusion period. Ca2+accumulated more in Ovx rat hearts than in sham-operated or Ovx+E2β hearts, and mitochondrial respiratory function was lower in Ovx hearts than in hearts from the other two groups. Marked interstitial edema and contraction bands were seen in hematoxylin-eosin-stained sections of Ovx rat hearts but not in hearts from either of the other groups. Hematoxylin-basic fuchsin-picric acid-stained sections revealed fewer viable myocytes in hearts from the Ovx group than from the sham or Ovx+E2β group. Transmission electron microscopy demonstrated more severely damaged mitochondria and ultrastructural damage to myocytes in Ovx rat hearts. Our results indicate that estrogen plays a cardioprotective role in global myocardial ischemia-reperfusion injury in female rats.
