Non-invasive analysis of bone mass in male and female growth-hormone transgenic mite, using dual energy X-ray absorptiometry

The aim of the present study was the non-invasive, sex-specific measurement of bone mass in bovine growth hormone (bGH) transgenic mice and normal con trols with dual energy X-ray absorptiometry (DXA). The transgenic mouse con stitutes a suitable animal model to study the influence of growth hormone o n the skeletal system. We analysed 28 animals, aged 12 weeks (14 transgenic , 14 controls, 7 male and 7 female, respectively), using a peripheral DXA s canner that had been adapted to the measurement of small animals. At a meas urement time of 20 min, the precision (RMS average CV %) was 4.4 % for bone mass (BMC), 2.5 % for areal bone density (BMD), 0.86 % for total body weig ht and 4.5 % for the percentage BMC (relative to body weight). While the ab solute bone mass was not significantly different between male and female an imals, we found a higher percentage of the BMC relative to the total bone m ass in females (+21% in controls, +31% in transgenics; p < 0.01). The absol ute bone mass was higher in the transgenic animals (+71% in females and +62 % in males; p<0,01), but relative to the body weight the transgenic females yielded similar and the transgenic males lower values (-7,2%; p<0.05). Usi ng DXA it is possible to non-invasively determine the mass of mineralised t issue in the mouse with relatively high precision and to effectively discri minate between different groups. Although a strong influence of growth horm one on the absolute bone mass is observed, the results show that this incre ase is not higher than that of the total body mass.