Effect of estrogen on global myocardial ischemia-reperfusion injury in female rats

We investigated the effects of estrogen on global myocardial ischemia-reper fusion injury in rats that were ovariectomized (Ovx), sham-operated, or ova riectomized and then given 17 beta -estradiol (E(2)beta) supplementation (O vx+E(2)beta). Hearts were excised, cannulated, perfused with and then immer sed in chilled (4 degreesC) cardioplegia solution for 30 min, and then retr ogradely perfused with warm (37 degreesC), oxygenated Krebs-Henseleit bicar bonate 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+E(2)b hearts. However, coronary flow ra tes or nitrate production were not consistently different throughout the en tire reperfusion period. Ca2+ accumulated more in Ovx rat hearts than in sh am-operated or Ovx+E(2)beta hearts, and mitochondrial respiratory function was lower in Ovx hearts than in hearts from the other two groups. Marked in terstitial edema and contraction bands were seen in hematoxylin-eosin-stain ed sections of Ovx rat hearts but not in hearts from either of the other gr oups. Hematoxylin-basic fuchsin-picric acid-stained sections revealed fewer viable myocytes in hearts from the Ovx group than from the sham or Ovx+E(2 )beta group. Transmission electron microscopy demonstrated more severely da maged mitochondria and ultrastructural damage to myocytes in Ovx rat hearts . Our results indicate that estrogen plays a cardioprotective role in globa l myocardial ischemia-reperfusion injury in female rats.