Greater Effect of Dietary Potassium Tripolyphoshate than of Potassium Dihydrogenphosphate on the Nephrocalcinosis and Proximal Tubular Function in Female Rats from the Intake of a High-phosphorus Diet

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We examined whether a difference in potassium dihydrogenphosphate (KH₂PO₄) and potassium tripolyphosphate (K₅P₃O₁₀) as dietary phosphorus sources could differentially effect the nephrocalcinosis and proximal tubular function in female rats. Rats were fed on a diet containing KH₂PO₄ or K₅P₃O₁₀, at the normal phosphorus level (normal phosphorus diet) or at a high phosphorus level (high-phosphorus diet) for 21 d. Nephrocalcinosis, as confirmed by a histological examination, was apparent in all rats fed on the high-phosphorus diet, and this condition was more severe in those rats fed on K₅P₃O₁₀ than in those fed on KH₂PO₄. As indicators of the proximal tubular function, the N-acetyl-β-D-glucosaminidase activity in urine and the urinary β₂-microglobulin excretion were significantly increased in those rats fed on the high-phosphorus diet containing K₅P₃O₁₀. These results indicate that the intake of a high-phosphorus diet, more strongly influenced the nephrocalcinosis and proximal tubular function when K₅P₃O₁₀ rather than KH₂PO₄ was used as the dietary phosphorus source.