High phosphate diet–induced kidney injury is exacerbated by low magnesium feeding. (A) Heminephrectomized mice were administered either a high phosphate (1.25%)/normal magnesium (0.05%) diet (n = 6), a high phosphate (1.25%)/low magnesium (0.005%) diet (n = 15), a low phosphate (0.25%)/normal magnesium (0.05%) diet (n = 6) or a low phosphate (0.25%)/low magnesium (0.005%) diet (n = 6) for 6 weeks. (B–D) Representative micrographs showing (B) PAS-, (C) Sirius Red– and (D) F4/80-stained kidney sections. Scale bars: 100 µm for PAS staining, 200 µm for Sirius Red staining and F4/80 staining. (E) Tubular injury scores and Sirius Red– and F4/80-positive areas were significantly increased by the high phosphate/low magnesium diet. (F) TGF-β1 and TNF-α mRNA expression levels in the whole kidney were upregulated in the high phosphate/low magnesium diet group. (G) Kaplan–Meier curves showing the significantly reduced survival rate in mice maintained on the high phosphate/low magnesium diet compared with the high phosphate/normal magnesium diet (P = 0.006; log-rank test). At 6 weeks, all mice in the high phosphate/normal magnesium diet group (n = 6) were alive, whereas only 4 of 15 mice in the high phosphate/low magnesium diet group were alive. Data are presented as the mean ± standard deviation. Differences between the two groups were compared using a Student’s t-test with a Bonferroni correction (NS, not significant; *P<0.05, **P<0.01).