Figure 2. mRNA levels of bone Cyp27b1 (encoding 1α(OH)ase activity) and Cyp24a1(encoding 24(OH)ase activity) and serum levels of 25(OH)D and 1,25(OH)₂D.

Total RNA was extracted from bone marrow–flushed femurs and mRNA levels of bone Cyp27b1 and Cyp24a1 were determined by RT-PCR and normalized to Gapdh mRNA (A). Data are the mean ± SEM of at least 3 independent experiments, n = 3–6/experiment. ****P < 0.0001 in adenine-treated WT mice compared with WT mice on a regular diet, determined by Student’s t test. Serum levels of 25(OH)D and (C) serum levels of 1,25(OH)₂D, as determined by ELISA, in WT mice, osteocyte-specific 1αOHase^–/– KO mice (Oct), and global 1αOHase^–/– KO mice (Global). (B). “Ad” indicates treatment with adenine. Global 1αOHase^–/– KO mice remained on a high calcium diet during the course of the experiments. “d” represents the detection limit of the assay for 1,25(OH)₂D. Data are the mean ± SEM (n = 6–8 mice of each genotype). **P ≤ 0.01 compared with mice of the same genotype on a non-adenine–containing diet, determined by ANOVA with Bonferroni multiple comparison test.