Hn. Rosen et al., SUBREGION ANALYSIS OF THE RAT FEMUR - A SENSITIVE INDICATOR OF CHANGES IN BONE-DENSITY FOLLOWING TREATMENT WITH THYROID-HORMONE OR BISPHOSPHONATES, Calcified tissue international, 55(3), 1994, pp. 173-175
Measurement of bone mineral density (BMD) by dual X-ray absorptiometry
(DXA) is a precise and accurate way to assess changes in BMD due to a
variety of causes. However, the degree of bone loss may vary dependin
g on the skeletal site examined. We postulated that interventions that
change bone density would have a different effect on an area rich in
trabecular bone, such as the distal femur, than on other subregions of
the femur. Male Sprague-Dawley rats (325-350 g) were treated with tri
iodothyronine (T-3), a bisphosphonate (pamidronate), or placebo for 21
days and then sacrificed. Ex vivo BMD of the proximal, distal, mid an
d total femur were measured by DXA. We found that mean BMD of hyperthy
roid rats was significantly lower than controls at all femoral subregi
ons. However, the difference in mean BMD between hyperthyroid and cont
rol rats was greatest at the distal femur (8.6%). In rats treated with
bisphosphonate, mean BMD was significantly higher than controls at th
e proximal, distal, and total femur. The difference in mean BMD betwee
n controls and rats treated with bisphosphonate was greatest at the di
stal femur (31.8%). Furthermore, pamidronate (APD)-treated rats had lo
wer mean mid-femur BMD than controls. We conclude that changes in BMD
after treatment with bisphosphonate or T-3 are greatest at the distal
femur subregion, and that treatment with bisphosphonate may cause a sl
ight reduction in mid-femur BMD. Future studies examining changes in B
MD in the rat femur after interventions that alter mineral metabolism
should include subregion analysis.