Figure 4.

Down-regulation of Cyp27b1 expression with age and Cyp27b1 heterozygous deletion results in 1,25(OH)₂D insufficiency. (A) Western blots of kidney, and intestine and bone extracts for the expression of Cyp27b1 in 3-, 9- and 18-month-old WT mice. ß-actin was used as loading control for Western blots. (B) Serum calcium, (C) phosphorus, (D) PTH, (E) 25(OH)D and (F) 1,25(OH)₂D levels in 9-month-old Cyp27b1 ^+/- mice and WT mice. (G) Cyp27b1 mRNA levels in vertebrae of 9-month-old Cyp27b1^+/- mice and WT mice were determined by real-time RT-PCR, and calculated as a ratio relative to Gapdh mRNA. Results are shown relative to WT. Values are means ± SEM of 6 determinations per group. *P<0.05, **P<0.01, compared with WT mice.