Dual-energy X-ray absorptiometry (DXA), together with the use of ultra-high resolution software, recently appeared as an accurate method for determining bone mineral density (BMD) in the rat. In order to assess the ability of this technique to detect changes in bone mass in the rat rapidly and precisely, we measured BMD at various sites of the femur using DXA subregional analysis. In particular, we studied the BMD of the metaphyseal part of the femur (M-BMD) rich in trabecular bone, and compared the values obtained with the cancellous bone volume measured by histomorphometry. In short-term ovariectomized animals (experiment 1), M-BMD was the only parameter to differentiate statistically between 10 ovariectomized (OVX) and 10 SHAM-operated (SHAM) rats (−11.2%,p<0.01) 9 days after surgery. M-BMD still expressed the greatest variation between OVX and SHAM rats 42 days following ovariectomy (experiment 2) (−16.1%,p<0.001 v −6.2%,p<0.01 for the total femur BMD) and confirmed previous data demonstrating a greater loss of cancellous than cortical bone after cessation of ovarian activity. M-BMD was highly correlated with cancellous bone volume (BV) in normal (r=0.82,p<0.001,n=30), OVX (r=0.77,p<0.001,n=22) and SHAM (r=0.88,p<0.001,n=21) rats. Furthermore, subcutaneous treatment with rat parathyroid hormone fragment (1–34) (r-PTH(1-34)) partially and significantly protected animals from trabecular osteopenia induced by OVX; there was a similar degree of protection of BV and M-BMD (50% and 61% respectively), while BMD of the entire femur achieved complete protection. This M-BMD measurement, specifically reflecting cancellous bone mass as confirmed by the correlation study and the response to PTH treatment, is a sensitve and simple method which can be used to assess any precocious modifications of bone density under physiopathological or therapeutic conditions in experimental rat models of bone loss.
Absorptiometry Dual-energy X-ray absorptiometry Histomorphometry Ovariectomy Rat