The Long-term Effect of High Phosphate Intake on Parathyroid Cell Proliferation in Chronic Renal Failure Rats

Abstract

: Most studies on the effect of phosphorous on parathyroid cell proliferation were performed only on short duration and long-term observation has not been reported. Therefore, the present study was undertaken to assess the long-term effect of high phosphorous intake on cell proliferation in the parathyroid gland of chronic renal failure rats. Rats were made uremic by the procedure of 5/6 Nephrectomy and then were divided into two groups : group 1 received a high phosphorus diet containing 1.2% phosphorous and 1.2% calcium, and group 2 received a normal phosphorus diet containing 0.5% phosphorous and 0.6% calcium. The control group comprised normal rats receiving a normal level of phosphorous in their diets, and was denoted group 3. Six, 9 and 16 weeks after the partial nephrectomy, 5 rats from each group were sacrificed and samples of blood, 24-hour urine, and parathyroid tissue were taken. Sections of parathyroid gland were immunostained for proliferative cell nuclear antigen (PCNA) to assess parathyroid cell proliferation. A diet high in phosphorous was shown to significantly accelerate parathyroid cell proliferation in CRF rats (P< 0.05) at each time point studied, and serum intact parathyroid hormone significantly increased in parallel with parathyroid cell proliferation (P< 0.05). This study demonstrates that a long-term intake of high phosphorous levels may mediate the development of continuous cell proliferation of the parathyroid gland with the subsequent development of secondary hyperparathyroidism.