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Osteopenic Changes Induced by Ovariectomy or Combination Unloading and Ovariectomy in Aged Rats
Author(s) -
Tou Janet,
Arnaud Sara,
Brown Marybeth,
Foley Andrea,
Wade Charles
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1062-b
Subject(s) - ovariectomized rat , osteopenia , endocrinology , medicine , estrogen , bone mineral , femur , osteoporosis , hindlimb , bone density , surgery
Techniques for measuring bone strength and age of the animal used are important factors to consider in models of bone loss. Previously, we reported that the combination of reduced estrogen and mechanical load increased the severity of osteopenia in mature (6 months) rats. The objective of this study was to determine the effect of estrogen withdrawal or the combination of reduced estrogen and mechanical load on bone in an aged rat model. Aged (18 months old) Sprague‐Dawley rats (n=7–8/group) were sham‐operated (Sham), ovariectomized (OVX) or OVX then hindlimb unloaded (HU/OVX) for 4 weeks. OVX reduced bone mineral density (BMD) non‐significantly (6.6%) whereas combined HU/OVX significantly (P=0.01) decreased BMD by 10.6% compared to Sham rats. Similarly, OVX reduced bone mineral content (BMC) non‐significantly (6.2%) whereas HU/OVX significantly (P=0.001) decreased BMC by 14.7% compared to Sham rats. No bilateral differences in femoral BMD and BMC were noted. Bone strength was determined by torsion test on the left femur and three‐point bending test on the right femur. By torsion test, HU/OVX of rats reduced femoral strength by 15.7% (P<0.040) compared to Sham animals. By bending test, peak force, ultimate bending strength and Young's Modulus in HU/OVX was reduced (P<0.05) compared to both Sham and OVX animals. The results indicate that major decreases in bone do not occur unless decreased estrogen is accompanied by mechanical unloading. The study findings are important because declining sex steroid concentrations during aging is often accompanied by decreased physical activity.