Figure 5.

Circulating FGF23 levels, are reduced in non-uremic mice deficient in osteoblastic 1(OH)ase and are increased by exogenous 1,25(OH)₂D but not 25(OH)D. Serum biochemistry of OB-1(OH)ase^−/− mice. WT and OB-1(OH)ase^−/− mice were maintained on normal chow and were euthanized at 3 months of age. Blood was collected for biochemical assays as described in Concise Methods. Serum 1,25(OH)₂D (A), Ca (B), P (C), PTH (D), FGF23 (E), 25(OH)D (F), and 24,25(OH)₂D (G) are shown in WT, 1(OH)ase^−/−C, and OB-1(OH)ase^−/− mice after treatment with vehicle (V) or with exogenous 1,25(OH)₂D (6 ng/g every 2 days for 1 week) or with 25(OH)D (100 ng/g every 2 days for 1 week). Bars represent the mean±SEM of 6–8 animals per group; significant differences between groups were determined by one-way ANOVA followed by Bonferroni test. *P≤0.05; ***P<0.001; and ****P≤0.001 relative to mice of the same genotype on the same diet; ^‡P≤0.05; ^‡‡P≤0.01; and ^‡‡‡‡P≤0.001 compared with WT mice.