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Adverse effects of hyperphosphatemia on myocardial hypertrophy, renal function, and bone in rats with renal failure
Katia R Neves1, Fabiana G Graciolli, Luciene M dos Reis
1Nephrology and Pathology Division, University of São Paulo, São Paulo, SP, Brazil.
Insights
High phosphorus levels in chronic renal failure (CRF) cause heart enlargement and worsen kidney function, even with parathyroid hormone (PTH) treatment. Phosphorus control is crucial for reducing complications in CRF patients.
Area of Science:
- Nephrology
- Cardiovascular Physiology
- Bone Metabolism
Background:
- Hyperphosphatemia and mineral metabolism disturbances are common in chronic renal failure (CRF).
- These imbalances contribute to cardiovascular disease and renal osteodystrophy.
- The study investigates the impact of hyperphosphatemia on cardiovascular, renal, and bone health in experimental uremia.
Purpose of the Study:
- To evaluate the effects of hyperphosphatemia on the cardiovascular system in CRF.
- To assess the impact of hyperphosphatemia on renal function.
- To determine the influence of hyperphosphatemia on bone remodeling in experimental uremia.
Main Methods:
- Wistar rats underwent parathyroidectomy (PTx) and 5/6 nephrectomy (Nx) with or without parathyroid hormone (PTH) replacement.
- Animals were fed either low-phosphorus (LP) or high-phosphorus (HP) diets.
- Measurements included weekly blood pressure, body weight, and post-mortem biochemical, histological, and bone histomorphometry analyses.
Main Results:
- High-phosphorus diets significantly increased heart weight normalized to body weight in PTx + Nx rats.
- Serum creatinine levels were elevated in rats on high-phosphorus diets, indicating impaired renal function.
- Bone histomorphometry showed decreased trabecular connectivity associated with high-phosphorus diets, independent of uremia.
Conclusions:
- Hyperphosphatemia is linked to myocardial hypertrophy, renal dysfunction, and detrimental bone changes in this model.
- Parathyroid hormone (PTH) replacement did not mitigate these adverse effects.
- These findings highlight the critical importance of phosphorus management in reducing morbidity and mortality in chronic renal failure (CRF) patients.
Background:
Hyperphosphatemia and disturbances in calcium or parathyroid hormone (PTH) metabolism contribute to the high incidence of cardiovascular disease and renal osteodystrophy in chronic renal failure (CRF). We evaluated the effect of hyperphosphatemia on the cardiovascular system, on renal function, and on bone in experimental uremia.
Methods:
Wistar rats were submitted to parathyroidectomy (PTx) and 5/6 nephrectomy (Nx) with minipump implantation, delivering 1-34 rat PTH (physiologic rate), or were sham-operated and received vehicle. Only phosphorus content (low-phosphorus (LP) 0.2%; high-phosphorus (HP) 1.2%) differentiated diets. We divided the groups as follows: PTx +Nx +LP; sham + LP; PTx + Nx + HP; and sham + HP. Tail-cuff pressure and weight were measured weekly. After 2 months, biochemical, arterial, and myocardial histology and bone histomorphometry were analyzed.
Results:
Heart weight normalized to body weight (heart weight/100 g body weight) was higher in PTx + Nx + HP rats (PTx + Nx + HP = 0.36 +/- 0.01 vs. sham + HP = 0.29 +/- 0.01, PTx + Nx + LP = 0.32 +/- 0.01, sham + LP = 0.28 +/- 0.01) (P < 0.05). Serum creatinine levels were higher in PTx + Nx + HP rats than in PTx + Nx + LP rats (1.09 +/- 0.13 vs. 0.59 +/- 0.03 mg/dL) (P < 0.05). Levels of PTH did not differ significantly between the groups. Myocardial and arterial histology detected no vascular calcification or fibrosis. Bone histomorphometry revealed an association, unrelated to uremia, between HP diets and decreased trabecular connectivity.
Conclusion:
Myocardial hypertrophy, impaired renal function, and adverse effects on bone remodeling were associated with hyperphosphatemia and were not corrected by PTH replacement. Although no vascular calcification was observed in this model, we cannot rule out an adverse effect of hyperphosphatemia on the vascular bed. Our finding underscores the importance of phosphorus control in reducing morbidity and mortality in CRF patients.
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