Effects of ovariectomy on bone morphology in maxillae of mature rats

Postmenopausal oestrogen deficiency results in bone loss (osteoporosis) in humans and experimental animals. The loss of trabecular bone in the ovariec tomized (OVX) rat provides a useful experimental model of postmenopausal os teoporosis. At 5 months after ovariectomy of 3-month-old female rats, the m id and distal femurs and maxillae were dissected and processed for quantita tive backscattered electron microscopic examinations. Histomorphometric ana lysis of femurs in OVX rats showed significant loss in metaphyseal trabecul ar bone areas compared with sham-operated controls; no significant bone los s was observed in the cortical bone areas of mid-diaphyses in OVX rats. Net bone area in the maxillae of OVX rats was similar to that of sham-operated controls. Bone structure of maxillae in OVX rats was also similar to that in controls. Our results suggest that, in this animal model of osteoporosis , prominent bone loss occurs mainly in the bone areas formed by endochondra l ossification such as distal femurs, but those areas formed by intramembra nous ossification such as mid-femurs and maxillae sustained less effects by OVX.