Figure 4.

Active vitamin D compounds and cinacalcet normalize osteoblast activity but cinacalcet, and not active vitamin D compounds, increases osteoclasts. Bone turnover is shown: in wild-type (WT) mice; in 1α(OH)ase null mice [1α(OH)ase^−/−] on a high-calcium intake (h) treated with vehicle, 1,25(OH)₂D₃, doxercalciferol, and cinacalcet; in 1α(OH)ase null mice on a rescue diet (r) treated with vehicle, and cinacalcet. (A) Osteoblast surface relative to bone surface (OB.S/BS); (B) serum osteocalcin concentrations; (C) osteoclast numbers relative to bone perimeter [N.Oc/bone perimeter (mm)]; (D) serum concentrations of TRAP5b. Each value is the mean ± SEM. Number of replicates for OB.S/BS from left to right are as follows: 4 for WT, 5 for vehicle, 5 for 1,25(OH)₂D₃, 5 for doxercalciferol, 5 for cinacalcet, 7 for vehicle, and 6 for cinacalcet. Number of replicates for osteocalcin from left to right are as follows: 5 for WT, 3 for vehicle, 4 for 1,25(OH)₂D₃, 5 for doxercalciferol, 3 for cinacalcet, 6 for vehicle, and 5 for cinacalcet. Number of replicates for N.Oc/bone perimeter from left to right are as follows: 3 for WT, 4 for vehicle, 7 for 1,25(OH)₂D₃, 5 for doxercalciferol, 5 for cinacalcet, 8 for vehicle, and 12 for cinacalcet. Number of replicates for serum TRAP5b from left to right are as follows: 4 for WT, 3 for vehicle, 3 for 1,25(OH)₂D₃, 3 for doxercalciferol, 3 for cinacalcet, 3 for vehicle, and 4 for cinacalcet. ⁺P < 0.05 relative to WT mice; ⁺⁺P < 0.01 relative to WT mice; ⁺⁺⁺P < 0.001 relative to WT mice; *P < 0.05 relative to vehicle-treated 1α(OH)ase null mice on a high-calcium intake; **P < 0.01 relative to vehicle-treated 1α(OH)ase null mice on a high-calcium intake; ***P < 0.001 relative to vehicle-treated 1α(OH)ase null mice on a high-calcium intake; ^○P < 0.05 relative to vehicle-treated 1α(OH)ase null mice on a rescue diet. ^○○○P < 0.001 relative to vehicle-treated 1α(OH)ase null mice on a rescue diet. ^●●P < 0.01 relative to cinacalcet-treated 1α(OH)ase null mice on a high-calcium intake.