Osteopenia develops in experimental animals following surgical removal of the ovaries (
ovariectomy. Ovx) or the stomach (
gastrectomy, Gx). Though the effect of Ovx has been ascribed to
estrogen deficiency, the mechanism behind the Gx-evoked
osteopenia remains unknown. In order to compare Gx- and Ovx-evoked
osteopenia, young female rats were subjected to Ovx, gx, the combination of ovx and Gx, or
sham operation (
SHAM). Serum osteoclast-derived
tartrate-resistant acid phosphatase 5b was measured as an index of
bone resorption, and serum
osteocalcin as an index of bone formation/turnover.
Bone resorption predominated over bone formation during the first 4 days after Ovx but not later.
Bone resorption predominated over bone formation throughout the first 4-week period after Gx. the changes were not additive in the ovx+Gx group. Transillumination and histomorphometry of the calvariae revealed extensive
osteopenia in the Gx and the Ovx+Gx groups but not in the Ovx group. Peripheral quantitative computerized tomography of the femur metaphysis showed a decrease in the trabecular bone
mineral density (BMD) in all three groups although Ovx+Gx seemed to induce greater trabecular bone loss than Gx alone. However, dual energy X-ray absorptiometry (DXA) of the intact femurs revealed reduced bone mineral content (BMC) in the Gx and Ovx+Gx groups but not in the Ovx group. Indeed, cortical bone was impaired by Gx and Ovx+Gx but not by Ovx. Hence, it seems clear that the Gx-evoked
osteopenia differs from that induced by Ovx but that the
osteopenia induced by Ovx+Gx is only marginally greater than that induced by Gx alone.