Renin upregulation is independent of the calcium status. (a and b) Blood ionized calcium levels (a) and serum iPTH concentrations (b) in wild-type (white bars) and VDR^–/– (black bars) mice at 20 days of age, at 3 months of age, or treated with the HCa-Lac diet for 5 weeks (5 wks Ca). *P < 0.01 vs. corresponding wild-type value; n ≥ 5 in each group. Note that the white bars are barely visible in b. (c) Northern blot analysis of renal renin mRNA from 20-day-old wild-type and VDR^–/– mice. (d) Quantitative data of the Northern blot analyses from 20-day-old mice. *P < 0.001 vs. wild-type mice. (e) Northern blot analysis of renin mRNA expression in the kidney of wild-type and VDR^–/– mice treated with the HCa-Lac diet for 5 weeks. (f) Quantitative result of the Northern blot analysis in shown in e. *P < 0.001 vs. wild-type mice. (g) Plasma Ang II concentrations of the mice analyzed in e. *P < 0.01 vs. wild-type mice; n = 5 in each genotype.