Changes in the Renal Copper Concentration in Rats as a Function of Phosphorus Intake

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We have found that the renal copper concentrations are markedly decreased in rats fed a low-phosphorus diet or administered phosphate binders. To clarify the relationship between phosphorus intake and renal copper concentration, we examined the renal copper concentrations in rats fed three types of diet with different phosphorus content. Eighteen 4-week-old male Wistar rats were divided into 3 groups and fed either a low phosphorus diet (phosphorus concentration, 0.15%), a control diet (phosphorus concentration, 0.3%), or a high phosphorus diet (phosphorus concentration, 0.6%) for 4 weeks. The serum phosphorus concentration reflected the phosphorus intake, with the highest values in the high phosphorus diet group, control group, and low phosphorus diet group, in that order. In the liver, the low phosphorus diet group had a significantly lower copper concentration than the other two groups, but the difference was not large. The kidney copper concentrations were remarkably different among the groups, with the highest values in the high phosphorus diet group, control group, and low phosphorus diet group, in that order. There were no differences in the iron, zinc, and manganese concentrations among the groups, except for a higher liver iron concentration in the low phosphorus diet group. These results indicate that the renal copper concentration increases or decreases specifically in response to changes in the phosphorus intake.