Nephrocalcinosis in Female Rats Fed Diets Containing Either Pectin or Cellulose

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Problem statement: There is evidence that the type of fiber influences the development of nephrocalcinosis in rats, but the effect of pectin was unknown. Approach: The effects of dietary pectin and cellulose on kidney calcification were studied in female rats. The diets used contained either 0.4-0.6% phosphorus and either cellulose (10%, w/w) or pectin. The purified diets used were balanced for residual calcium, magnesium and phosphorus in the fiber preparations. Results: Increasing the phosphorus concentration of the diet from 0.4-0.6% caused massive nephrocalcinosis in rats fed the cellulose diets. Pectin (10%, w/w) versus cellulose in diets containing 0.4% phosphorus significantly increased calcium and phosphorus concentrations in kidney. When compared with cellulose, pectin did not influence the apparent absorption of calcium, phosphorus and magnesium. Urinary concentrations of calcium and magnesium were not affected by pectin feeding, but those of phosphorus were increased. When pectin was given with the diet containing 0.6% phosphorus, its nephrocalcinogenic action as compared with cellulose was not observed. Conclusion: Pectin instead of cellulose in diets containing 0.4% phosphorus induced nephrocalcinosis in female rats. The effect of pectin may be explained by an increase in urinary phosphorus concentration. The lack of nephrocalcinogenic action of pectin in a diet with 0.6% phosphorus indicates that the nephrocalcinosis-inducing effect of high phosphorus intake had overruled any effect of fiber type.