A micropuncture study of renal phosphate transport in rats with chronic renal failure and secondary hyperparathyroidism.
AUTOR(ES)
Bank, N
RESUMO
Micropuncture studies were carried out in rats to determine changes in tubular transport of phosphate which occur in chronic renal failure and secondary hyperparathyroidism. Rats underwent subtotal nephrectomy (NX) and were fed a low calcium, high phosphorus diet for 3--4 wk. Other groups consisted of normal control animals, normal rats infused with sodium phosphate to raise filtered load of phosphate, subtotal NX rats parathyroidectomized (PTX) on the day of experiment, and normal PTX rats infused with sodium phosphate. It was found that filtered phosphate/nephron is markedly increased in subtotal NX rats due to high single nephron filtration rates, proximal tubular fluid plasma phosphate ratios are less than 1.0, and fractional reabsorption of phosphate is decreased in the proximal tubule. More phosphate was present in the final urine than in surface distal convoluted tubules. Acute PTX in subtotal NX rats resulted in a striking increase in proximal phosphate reabsorption, and urinary phosphate became approximately equal to that remaining in surface distal tubules. Phosphate loading in normal rats reduced fractional reabsorption in the proximal tubule, but urinary phosphate was not greater than that at the end of surface distal tubules. Acute PTX in normal phosphate-loaded animals had no significant effect on proximal tubular phosphate reabsorption. These observations suggest that phosphate homeostasis in chronic renal failure is acheived by inhibition of proximal phosphate reabsorption, counteracting a greatly enhanced intrinsic capacity for reabsorption. In addition, the large amount of urinary phosphate is consistent either with secretion by the collecting ducts or with a disproportionately high contribution by deep nephrons. The changes in phosphate transport are mediated by parathyroid hormone and are completely abolished by acute removal of the hormone.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=372607Documentos Relacionados
- Erythrocyte survival in chronic renal failure. Role of secondary hyperparathyroidism.
- Progressive renal failure in surgically treated hyperparathyroidism.
- Subtotal versus total parathyroidectomy with forearm autograft for secondary hyperparathyroidism in chronic renal failure.
- Circulating forms of parathyroid hormone detected with an immunofluorometric assay in patients with primary hyperparathyroidism and in hyperparathyroidism secondary to chronic renal failure
- Rapid progression of mitral and aortic stenosis in a patient with secondary hyperparathyroidism.