Response of the Rat Heart to Bilateral Ovariectomy and Estrogen

ABSTRACT

BACKGROUND AND OBJECTIVES: Although ovarian estrogen is believed to decrease coronary heart disease by improving plasma lipoprotein and enhancing vasodilation, estrogen effect on heart tissue has not been shown yet. So we investigated the effect of the ovariectomy and estrogen on rat heart tissue. MATERIALS AND METHODS: Female Sprague Dawley rats, about 3 months of age, were subjected to sham surgery (n=9) or bilateral ovariectomy (n=20) and maintained untreated for 8 weeks after surgery. We administered estrogen (20 mg/Kg subcutaneously, 3 times/week) to 10 ovariectomized rats for 4weeks; the remaining ovariectmized rats received only saline. Animals were divided in 3 groupgroup 1 (control); sham op, group 2; ovariectomized only, group 3; ovariectomy+estrogen. We measured left ventricular thickness [IVS+LVPW)/2] and number of cardiomyocytes and interstitial fibrosis on light microscope (H & E and Masson's trochrome stain) and electron microscope. RESULTS: 1) LV wall thicknesses were significantly increased in group 2 and group 3 as compared with group 1 (2.45+/-0.1 and 2.46+/-0.11 vs 2.31+/-0.15 mm). 2) There were no significant change in the number of cardiomyocyte between group 1, group 2 and group 3 (54.3+/-5.7, 60.2+/-19.4, 52.5+/-14.1). 3) Group 2 and group 3 show more interstitial edema (44% and 62.5% vs 0%) on LM and more interstitial edema and the increase of number of mitochondria on EM than group 1. CONCLUSION: Bilateral ovariectomized rats show the increase of LV wall thickness, which was caused by interstitial edema without cardomyocyte hypertrophy and these changes were not reversed by the short-term administration of estrogen for 4 weeks.