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Progesterone antagonist RU 486 has bone-sparing effects in ovariectomized rats
E I Barengolts1, P V Lathon, F G Lindh
1Section of Endocrinology and Metabolism, University of Illinois College of Medicine, Chicago, USA.
Bone
|July 1, 1995
Summary
Medroxyprogesterone (MPA) and RU 486, a synthetic antiprogesterone, both preserved bone mass in ovariectomized rats. RU 486 showed agonist-like effects, but acted as a partial antagonist when combined with MPA.
Area of Science:
- Endocrinology
- Bone Biology
- Pharmacology
Background:
- Progesterone is known to prevent bone loss following ovariectomy.
- RU 486 is a synthetic steroid with antiprogesterone activity in reproductive tissues.
Purpose of the Study:
- To evaluate the effects of RU 486 on bone in sham-operated rats.
- To compare the effects of medroxyprogesterone (MPA), RU 486, and a combination of MPA and RU 486 in ovariectomized rats.
Main Methods:
- Ovariectomized and sham-operated rats were treated with MPA, RU 486, both, or vehicle for 4 weeks.
- Bone histomorphometry was performed on proximal tibial metaphysis.
Main Results:
- Ovariectomy led to lower trabecular bone volume and higher bone turnover.
- Both MPA and RU 486 treatments increased trabecular bone volume in ovariectomized rats.
- RU 486 demonstrated agonist-like effects, while its combination with MPA attenuated MPA's bone-preserving effects.
Conclusions:
- RU 486 exhibits bone-protective effects in ovariectomized rats, similar to MPA.
- RU 486 may act as a partial antagonist to exogenous progesterone in bone tissue.