Phosphate depletion arrests progression of chronic renal failure independent of protein intake

Following 5/6 nephrectomy, 18 rats were fed a normal diet. After 30 days, serum creatinine (SCr), urine protein excretion and urine volume were increased compared to pre-nephrectomy (0.27 +/- 0.1 vs. 1.62 +/- 0.6 mg/deciliter, 17.0 +/- 10.3 vs. 257.6 +/- 13.4 mg/24 hr, and 16.6 +/- 4.4 vs. 39.2 +/- 11.7 ml/24 hr, respectively, all P less than 0.001). At this time, when serum phosphorus (SPi) and serum calcium (SCa2+) were normal, the rats were separated into two groups, matched and paired by body weight and SCr, and housed separately in metabolic cages. Animals of one group ingested a normal diet supplemented with dihydroxyaluminum aminoacetate (DHAAA), 15 g%, to induce phosphate depletion (PD). The second group ingested the same diet supplemented with 7.5% glycine and was the phosphate replete (PR) group. All rats were pair fed throughout the study to maintain similar caloric, protein, carbohydrate, vitamin, and mineral intakes. At six weeks after separation, SPi was decreased in PD vs. PR group (2.85 +/- 0.8 vs. 6.71 +/- 1.2 mg/deciliter, P less than 0.001) and SCa2+ was increased in the PD group (11.98 +/- 0.7 vs. 10.03 +/- 0.7 mg/deciliter, P less than 0.001). Urine urea nitrogen, body weight, and sodium, potassium and solute excretion were similar between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)