Effects of Physiologic Concentration of Estrogen on Ischemia/Reperfusion-induced Apoptosis in Rat Myocardium

Kim, Hyo Soo; Kang, Hyun Jae; Kim, Young Kwon; Youn, Tae Jin; Chae, In Ho; Sohn, Dae Won; Oh, Byung Hee; Lee, Myoung Mook; Park, Young Bae; Choi, Yun Shik; Lee, Young Woo

Abstract

BACKGROUND: Ischemia/reperfusion injury is very important issue in the era of thrombolysis and primary coronary angioplasty in acute myocardial infarction. However, the mechanism of ischemia-reperfusion injury is not fully clarified. Estrogen is well known to have protective actions against ischemic heart disease. We tested hypothesis that estrogen may protect myocardium by reducing ischemia/reperfusion-induced apoptosis.
METHODS
Sprague-Dawley rats that underwent ovariectomy, female controls, and male rats were subjected to 45minutes of left coronary artery occlusion followed by 4 or 24hours of reperfusion. Coronary artery occlusion was performed 1 week after ovariectomy or sham operation. And sham operation was also performed in each group to confirm the effects of ischemia/reperfusion.
RESULTS
Ischemia/reperfusion induced apoptosis in myocardium, especially at border zone, whereas sham operation did not induce apoptosis. After 4 hours of reperfusion the percentages of apoptotic myocytes in border and center zone of reperfused area were 35.7+/-3.7%, 29.0+/-4.2% in ovariectomized rats (n=3), 40.8+/-3.7%, 29.5+/-2.5% in female control rats (n=3), and 39.0+/-1.6% (p=0.10), 32.4+/-1.6% (p=0.43) in male rats (n=3). After 24hours of reperfusion the percentages in border and center zone of reperfused area were 20.6+/-3.1%, 12.9+/-4.8% in ovariectomized rats (n=3), 19.6+/-4.1%, 14.0+/-2.0% in female control rat (n=3), and 21.4+/-6.6% (p=0.93), 15.1+/-2.4% (p=0.85) in male rats (n=3). There is difference of apoptosis neither between male and female rats nor between control and ovariectomized female rats.
CONCLUSION
Estrogen did not affect the ischemia/reperfusion-induced apoptosis in rat myocardium.