Table 3.

Serum biochemistry and phosphate-related hormones with age in normal rats

Parameters	4 weeks old	9 weeks old	15 weeks old
Phosphate (mg/dL)	9.6 ± 0.2	6.6 ± 0.2*	5.6 ± 0.1*,**
Calcium (mg/dL)	10.5 ± 0.1	10.4 ± 0.1*	10.1 ± 0.1*,**
BUN (mg/dL)	15.5 ± 0.5	18.1 ± 0.3*	17.9 ± 0.4*,**
Creatinine (mg/dL)	0.04 ± 0.01	0.07 ± 0.01*	0.15 ± 0.01*,**
FGF23 (pg/mL)	309 ± 34	457 ± 35*	689 ± 60*,**
Intact PTH (pg/mL)	370 ± 22	279 ± 73*	167 ± 8*,**
Calcitriol (pg/mL)	311 ± 29	219 ± 16*	74 ± 12*,**

Values are expressed as mean ± SE (n = 12).

^*P < 0.05, significant difference versus 4 weeks old.

^**P < 0.05; significant difference versus from 9 weeks old (Tukey–Kramer test).