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Prostaglandin E 2 (PGE 2 ) and Risedronate Was Superior to PGE 2 Alone in Maintaining Newly Added Bone in the Cortical Bone Site After Withdrawal in Older Intact Rats
Author(s) -
Ma Yan Fei,
Lin Bai Yun,
Jee Webster S. S.,
Lin Chao Hua,
Chen Yong Yong,
Ke Hua Zhu,
Li Xiao Jian
Publication year - 1997
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.1997.12.2.267
Subject(s) - cortical bone , prostaglandin e2 , diaphysis , prostaglandin e , microgram , endocrinology , medicine , tibia , bone formation , bone remodeling , prostaglandin , chemistry , anatomy , surgery , femur , in vitro , biochemistry
The objects of this study were (1) to determine the effects of risedronate (Ris) and prostaglandin E 2 (PGE 2 ) alone and in combination, on tibial diaphyses of older intact female rats; and (2) to observe the fate of any extra bone if formed after withdrawal of the treatment. Nine‐month‐old female Sprague‐Dawley rats were treated with 6 mg of PGE 2 /kg/day, 1 or 5 μg of Ris/kg twice a week, or 6 mg of PGE 2 /kg/day plus 1 or 5 μg of Ris/kg twice a week for the first 60 days and followed by vehicle injections for another 60 days. Cross‐sections of double fluorescent labeled, undecalcified tibial diaphyses proximal to the tibiofibular junction were processed for histomorphometry. We found that: (1) neither the 1 μg nor the 5 μg of Ris treatment in the 60‐day on/60‐day off group showed any histomorphometric differences from age‐related controls; (2) while the 60 days of PGE 2 treatment added extra cortical bone (6%) on the tibial shaft (due to stimulation of periosteal, endocortical, and marrow trabecular bone formation), the new endocortical and most of the new marrow trabecular bone were lost when treatment was withdrawn; however, the new periosteal bone remained; (3) PGE 2 with Ris added the same amount of new bone to tibial diaphysis as did PGE 2 alone and upon withdrawal, new marrow trabecular bone was lost but new periosteal and endocortical bones were preserved in PGE 2 + 1 μg of Ris on/off group. In contrast, all the new bone was maintained in the PGE 2 + 5 μg of Ris on/off group; (4) PGE 2 + Ris cotreatment failed to block the increase in cortical bone porosity induced by PGE 2 ; and (5) in the PGE 2 alone and PGE 2 + 1 μg of Ris on/off groups bone turnover was higher than that in the PGE 2 + 5 μg of Ris on/off group. These results indicate that on/off treatment with PGE 2 and Ris is superior to PGE 2 alone in that it forms the same amount of new bone during treatment, but preserves more cortical bone during withdrawal. Depression of bone resorption and turnover were the tissue mechanisms responsible for this protection.