Figure 1.

Circulating FGF23 is influenced by serum calcium and VDR levels. Basal serum biochemical parameters of WT, VDR^−/−, and 1(OH)ase^−/− mice. Serum Ca, P, PTH, and FGF23 are shown in panels (A–D), respectively. WT mice were maintained on normal chow. 1(OH)ase^−/− and VDR^−/− mice were maintained either on a high-Ca diet or a rescue diet, denoted as 1(OH)ase^−/−C and VDR^−/−C, and 1(OH)ase^−/−R and VDR^−/−R, respectively. Bars represent the mean±SEM of measured data from six to eight animals of each genotype. ^♦♦♦P < 0.001 compared with age-matched WT; ***P<0.001 and **P≤0.01 compared with mice of the same genotype on a high-Ca diet.