Figure 4.

Effect of alendronate and parathyroidectomy on osteocyte density in wild-type and D4 mice at day 35. Mice were treated with alendronate or vehicle starting at day 15 and underwent parathyroidectomy or sham operation at day 21. Untreated mice were the same as those analyzed in Figure 3. Values represent the mean ± SD. (A) Osteocyte density in the distal epiphysis of the femur, where bone resorption is present. Osteocyte densities in D4 mice treated with alendronate and sham operation (n = 3; ∗), or alendronate and parathyroidectomy (n = 6; ∗) were significantly reduced compared with untreated D4 mice (n = 5; p < 0.005). This reduction is more striking after calculation of the osteocyte formation rate (Figure 10). The osteocyte density in D4 mice treated with vehicle and parathyroidectomy (n = 4) was not significantly different from untreated D4 mice. Osteocyte densities in wild-type mice treated with vehicle and parathyroidectomy (n = 2), alendronate and sham operation (n = 3), or alendronate and parathyroidectomy (n = 6) were not significantly different from untreated wild-type mice (n = 6). (B) Osteocyte density in the diaphyseal cortex of the femur at the level of the third trochanter, where periosteal bone resorption is absent. Osteocyte densities were measured in only the subperiosteal 36 μm of cortical bone, which corresponds to periosteal bone made since day 21. The number of mice analyzed was as in panel A. Osteocyte densities in wild-type and D4 mice treated with alendronate and parathyroidectomy did not significantly differ from respective untreated wild-type and D4 controls.