A study on the trabecular change of Femur according to 17beta-Estradiol Dosage in Ovariectomized Rat

ABSTRACT

Osteoporosis is the consequence of an imbalance between osteoclastic and osteoblastic activity, coupled with an increased rate of bone turnover observed with menopause. Estrogen is generally considered to maintain bone mass through suppression of bone resorption. The purpose of this study was to evaluate the rat femoral trabecular change not only in the deficiency of estrogen but also in the administration of estrogen following ovariectomy(OVX). 30 female Sprague-Dawley rats were subjected to bilateral OVX or sham surgery(control). Groups of OVX were divided into 4 groups. The first group was injected daily with vehicle alone for 20 days after 20 weeks following OVX. The additional groups of OVX was injected daily with low, medium, or high doses of 17beta-estradiol(10, 25 or 50microgram/kg BW, respectively). All rats were sacrified 23 weeks after OVX, and their femur were processed for H&E, MT stain and histomorphometry. The results were as follows; 1. In the histomorphometric analysis, the trabecular bone volume/tissue volume, trabecular thickness and trabecular seperation were respectively 31.2+/-8.3%, 54.3+/-4.8micrometer and 280.7+/-16.4micrometer in vehicle treated OVX group and 48.6+/-7.3%, 90.4+/-4.5micrometer and 126.3+/-5micrometer in sham operation group, and they showed statistical significance compare to control group. 2. The trabecular bone volume/tissue volume, trabecular thickness and trabecular separation were respectively 44.4+/-4.3%, 109.5+/-12.3micrometer and 94.9+/-8.5micrometer in low doses of 17beta-estradiol injected group and they showed statistical significance compare to OVX group. 3. The trabecular bone volume/tissue volume, trabecular thickness and trabecular separation were respectively 44.4+/-4.3%, 109.5+/-12.3micrometer and 94.9+/-8.5micrometer in medium doses of 17beta-estradiol injected group and they showed statistical significance compare to OVX group, but they didn't show statistical significance compare to low doses of 17beta-estradiol injected group. 4. The trabecular bone volume/tissue volume, trabecular thickness and trabecular separation were respectively 46.4+/-4.5%, 154.4+/-13.2micrometer and 113.7+/-12.8micrometer in high doses of 17beta-estradiol injected group and they also showed statistical significance compare to OVX group, but they didn't show statistical significance compare to other experimental groups. From the above results, metaphyseal bone formation was markedly reduced in OVX rats but treatment of OVX rats with 17beta-estradiol resulted in normalization of femur trabecular bone volume. But they didn't show statistical significance the effect of bone formation according to the dose dependency.