The effects of various phosphate salts as the dietary phos-phorus sources on the development of nephrocalcinosis and kidney func-tion were examined in rats fed diets containing monophosphate salts (sodium dihydrogenphosphate, NaH
2PO
4, or potassium dihydrogen-phosphate, KH
2PO
4) or polyphosphate salts (sodium tripolyphosphate, Na
5P
3O
10, or potassium tripolyphosphate, K
5P
3O
10), at levels represent-ing normal phosphorus (normal phosphorus diet) or high phosphorus (high phosphorus diet) contents for 21d. High phosphorus diet-feeding increased the kidney calcium and phosphorus concentrations. Kidney calcium and phosphorus concentrations were higher in rats fed the high phosphorus diet containing Na
5P
3O
10 or K
5P
3O
10 than in rats fed the high phosphorus diet containing NaH
2PO
4 or KH
2PO
4. Nephrocalcinosis was observed in all rats fed a high phosphorus diet, and the degree of nephrocalcinosis was more severe in rats fed Na
5P
3O
10 or K
5P
3O
10 than in rats fed NaH
2PO
4 or KH
2PO
4. In rats fed the high phosphorus diet, creatinine clearance was higher in rats fed Na
5P
3O
10 or K
5P
3O
10 than in rats fed NaH
2PO
4 or KH
2PO
4. In rats fed Na
5P
3O
10 or K
5P
3O
10, urinary albumin excretion and
N-acetyl-β-D-glucosaminidase (NAG) activity in the urine were increased in rats fed the high phosphorus diet. These were higher in rats fed the high phosphorus diet containing Na
5P
3O
10 than in rats fed the high phosphorus diet containing NaH
2PO
4 or KH
2PO
4. This study observed that the development of nephrocalcinosis and kidney function in rats fed the high phosphorus diet was influenced by the difference in monophosphate or polyphosphate salts provided as the dietary phosphorus source, while the effects of sodium and potassium salts were not evident. We suggest that the development of nephrocalcinosis and kidney function in rats fed a high phosphorus diet was altered depending on the form of phosphate salts provided as the dietary source of phosphorus. Additionally, the development of nephrocalcinosis and diminished kidney function in rats fed the high phosphorus diet was more severe for polyphosphate salts as compared to monophosphate salts.
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