Figure 3.

Vitamin D (Vit D) deficiency lowers plasma 1,25(OH)₂D₃ and cerebral P-gp expression. a, C57BL/6 mice (8 weeks old) that were fed a vitamin D-deficient diet exhibited significantly lower (75%) plasma 1,25(OH)₂D₃ levels after 6 weeks of the diet (n = 4 for samples at 2, 4, and 6 weeks). Replenishment of the vitamin D-deficient mice after week 6 with dietary vitamin D or 1,25(OH)₂D₃ elevated plasma 1,25(OH)₂D₃ levels, albeit not to basal levels (n ≥ 6). b, Mdr1a mRNA expression and P-gp protein levels were fully restored on replenishment with 1,25(OH)₂D₃. For vitamin D-deficient and vitamin D-sufficient mice, n = 6. Data are mean ± SEM; a one-way ANOVA was used to evaluate differences between groups, with p values determined by Bonferroni's multiple comparisons test.