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Increased bone resorption precedes increased bone formation in the ovariectomized rat
N A Sims1, H A Morris, R J Moore
1Division of Clinical Biochemistry, Institute of Medical and Veterinary Science, Box 14, Rundle Mall Post Office, Adelaide, South Australia 5000.
Calcified Tissue International
|August 1, 1996
Summary
Ovariectomy in rats triggers early bone resorption markers, followed by increased bone formation and trabecular bone loss. This study tracks these bone changes over 42 days post-surgery.
Area of Science:
- Bone Biology and Endocrinology
- Skeletal Physiology
- Osteoporosis Research
Background:
- Ovariectomy (Ovx) is a common model for studying postmenopausal osteoporosis.
- Understanding the temporal sequence of bone resorption and formation is crucial for developing therapeutic strategies.
- Early detection of bone remodeling changes can inform interventions to prevent bone loss.
Purpose of the Study:
- To investigate the chronological sequence of biochemical and histomorphometric changes in bone metabolism following ovariectomy in rats.
- To determine the onset of increased bone resorption and formation markers relative to trabecular bone loss.
- To elucidate the local and systemic factors influencing bone remodeling dynamics post-ovariectomy.
Main Methods:
- Ovariectomy or sham surgery was performed on Sprague Dawley rats.
- Bone resorption markers (urinary hydroxyproline, ACP surface) and formation markers (serum osteocalcin, alkaline phosphatase, MAR) were measured at various time points.
- Trabecular bone volume (BV/TV) was assessed using histomorphometry in femora and lumbar vertebrae.
Main Results:
- Increased acid phosphatase (ACP) surface and urinary hydroxyproline excretion were observed as early as 6 days post-ovariectomy, indicating heightened bone resorption.
- Elevated serum osteocalcin and alkaline phosphatase activity, signifying increased bone formation, were detected at 9 days post-ovariectomy.
- Significant trabecular bone loss (decreased BV/TV) was evident in the femora by 15 days post-ovariectomy, preceding vertebral bone loss.
Conclusions:
- A systemic increase in bone resorption markers precedes enhanced bone formation in the ovariectomized rat model.
- Trabecular bone loss occurs following the initial surge in resorption and subsequent increase in formation.
- The rate of trabecular bone dissolution appears to be influenced by local factors, while systemic changes drive the initial resorption increase.