Table 2. Kidney calcium concentration, kidney calcium score and range of histochemical score for female and male Sprague-Dawley rats fed modified AIN-93G diets differing in calcium and phosphorus content for 16 wk1

Diet Kidney Ca1 Kidney Ca score (N/E/NC)2 Range of histochemical score3
µmol/g dry kidney
Female rats
AIN93 8.13 ± 2.75a (6.40–14.73) 7/1/0 0 to+
1.5x 10.90 ± 5.53ab (7.08–24.03) 3/5/0 0 to++
2.5x 23.10 ± 25.48bc (7.50–73.98) 2/6/0 0 to+++
4.0x 39.23 ± 31.05c (9.25–110.75) 0/7/1 + to+++
AIN76 171.08 ± 129.83* (31.63–445.43) 0/2/6 ++ to++++
Male rats
AIN93 7.63 ± 0.78 (7.08–9.45) 7/1/0 all 0
1.5x 7.58 ± 0.55 (7.05–8.83) 7/1/0 0 to+
2.5x 8.60 ± 1.55 (7.35–12.28) 6/2/0 all 0
4.0x 7.58 ± 1.28 (6.25–10.28) 7/1/0 0 to+
AIN76 8.23 ± 0.70 (7.25–9.03) 6/2/0 0 to+

1 Values are means ± SD (range), n = 8. a,b,c Values for female rats (diets AIN93 through 4.0x) bearing the same superscript were not significantly different by non-parametric Kruskal-Wallis ANOVA and Dunn’s multiple comparison test. * Value for female rats fed diet AIN76 different from AIN93 by nonparametric Mann-Whitney U test.

2 Classification of kidney calcium concentrations (by analysis). Number of rats with: N = Normal calcium content of rat kidney (for purposes of categorization of kidney Ca score in our laboratory, this is taken to be 7.50 ± 0.63 µmol/g dry kidney, mean ± SD, see also reference 5 ); E = Elevated calcium content, >8.75 µmol/g dry kidney (i.e., >normal + 2 SD) but <NC; NC = nephrocalcinosis, >75.0 µmol/g dry kidney (i.e., >10x Normal).

3 Based on number of granules seen in 1 transverse and 1 longitudinal kidney section (von Kossa stain): 0 = 0, + = 1–25, ++ = 26–75, +++ = 76–150, ++++ = >150.