Estradiol treatment transiently increases trabecular bone volume in ovariectomized rats

Area of Science:

• Endocrinology
• Bone Biology
• Pharmacology

Background:

• Ovariectomy in rats leads to increased bone turnover and subsequent bone loss.
• Estradiol plays a crucial role in regulating bone metabolism.

Purpose of the Study:

• To investigate the short-term effects of estradiol administration on bone turnover and bone loss following ovariectomy in rats.
• To determine the dose-dependent effects of estradiol on bone parameters.

Main Methods:

• Adult female Sprague-Dawley rats underwent ovariectomy.
• Daily subcutaneous injections of 17 beta-estradiol (low and high doses) or vehicle were administered.
• Femoral trabecular bone volume (BV/TV) and trabecular number (Tb.N) were measured.
• Serum alkaline phosphatase, urine hydroxyproline, and serum osteocalcin levels were analyzed.

Main Results:

• Estradiol transiently increased BV/TV and Tb.N in a dose-dependent manner at day 6 postoperation.
• Estradiol prevented the ovariectomy-induced decrease in BV/TV and Tb.N between days 9 and 15.
• High-dose estradiol maintained serum alkaline phosphatase and urine hydroxyproline at or below preoperative levels.
• Serum osteocalcin initially rose with estradiol but returned to baseline by days 15-21.

Conclusions:

• Estradiol administered from ovariectomy onset rapidly suppressed markers of osteoblast activity and bone resorption.
• Mineralization was not immediately suppressed, leading to a transient increase in bone volume and number.
• Short-term estradiol treatment effectively mitigates immediate post-ovariectomy bone loss in rats.