Phosphate excretion in the parathyroidectomized rat receiving parathyroid hormone

Stone, Jon; Hano, Jessie E.

doi:10.1016/0026-0495(72)90008-x

Cited by 6 publications

(2 citation statements)

References 19 publications

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“…Although the reason for the difference is not readily apparent, high dietary intake of phosphate in our dogs may be responsible for the higher proximal TF/UF phosphate in outr studies, since reducing intestinal absorption of phosphate by administration of aluminum-hydroxide gel resulted in a lower mean proximal TF/UF phosphate of 0.45.' Furthermore, Van Stone and Hano (37) showed that urinary excretion of phosphate increased similarly on increased dietary phosphate in both intact and PTX rats, indicating the importance of dietary phosphate intake on renal phosphate transport. Although the longer duration of TPTX in our animals, as compared to acutely PTX state studied by others, may also be responsible for the higher proximal TF/UF phosphate, our micropuncture data in acutely TPTX dogs (38), as well as those by Amiel, Kuntziger, and Richet (11) (39,40) and greater FR phosphate by the deep nephrons may be responsible for the difference in the remaining fractions between the superficial end proximal tubule and the final urine.…”

Section: Discussionmentioning

confidence: 97%

Micropuncture Studies of Phosphate Transport in the Proximal Tubule of the Dog THE RELATIONSHIP TO SODIUM REABSORPTION

Wen¹

1974

J. Clin. Invest.

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A B S T R A C T Micropuncture studies were performed in the dog to examine the relationship between sodium and phosphate transport in the proximal tubule. In hydropenic, thyroparathyroidectomized animals, administration of parathyroid extract, saline, or acetazolamide resulted in a fall in proximal tubule fluid-to-plasma (TF/P) inulin ratio as well as a rise in tubule fluid-toplasma ultrafilterable (TF/UF) phosphate ratio. A correlation was found between the changes in fractional reabsorption of sodium and phosphate but the phosphate changes were generally greater than those of sodium. Also, a high distal phosphate delivery in the face of low fractional excretion of phosphate in the urine in thyroparathyroidectomized dogs suggests significant phosphate reabsorption in the distal nephron. On the other hand, calcium chloride infusion to saline-loaded, normal dogs to suppress endogenous parathyroid hormone reduced proximal TF/UF phosphate without change in TF/P inulin, while both parameters remained unchanged in saline-loaded, thyroparathyroidectomized dogs after calcium infusion. An increase in proximal TF/UF phosphate associated with unchanged TF/P inulin was also demonstrated by administration of highly purified parathyroid hormone to saline-loaded, thyroparathyroidectomized dogs. It was concluded that although proximal tubule phosphate transport is generally closely related to that of sodium, the two can dissociate under certain experimental conditions, especially under the influence of parathyroid hormone. These observations also indicate that the effect of parathyroid hormone on proximal tubule phosphate transport is not solely dependent upon its effect on sodium transport.

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Section: Discussionmentioning

confidence: 97%

Micropuncture Studies of Phosphate Transport in the Proximal Tubule of the Dog THE RELATIONSHIP TO SODIUM REABSORPTION

Wen¹

1974

J. Clin. Invest.

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“…Such a mech anism has been shown to operate early in chronic renal failure such that plasma phos phate concentration is kept normal by in creasing concentrations of parathyroid hor mone which produce progressive decreases in renal phosphate reabsorption (21,22). How ever, the renal response to changes in dietary phosphate in animals with normal renal func tion occurs despite a constant blood concentra tion of parathyroid hormone (26), in parathyroidectomized animals (23,25). and in kid neys isolated from phosphate-restricted rats perfused with a synthetic albumin-containing solution (24).…”

Section: Resultsmentioning

confidence: 99%

Renal Response to Alterations in Dietary Phosphate in the Young Beagle

Russo¹,

Nash²

1980

Neonatology

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Hyperphosphatemia is present in the young of many species compared to adult animals. We studied the renal response to alterations in dietary phosphate in 4- to 7-day-old beagle puppies. Puppies were phosphate restricted with oral aluminum hydroxide gel (Group I) or phosphate loaded with oral sodium phosphate (Group II). Puppies in both groups had hyperphosphatemia (Group I 8.6, Group II 12.2mg/dl) relative to adult dogs (3.4–4.8 mg/dl). Plasma phosphate concentration (P) and rate of excretion of phosphate (Ep) were independent of glomerular filtration rate (GFR). At any filtered load of phosphate Ep was greater and rate of reabsorption less in Group II independent of P. The maximal rate of phosphate reabsorption (TmP) was higher in Group I (100 μg/ml GFR) than Group II (26 μg/ml GFR). Negative values for phosphate reabsorption in 4 animals support the presence of a secretory mechanism for phosphate. Relative hyperphosphatemia in the puppy is not secondary to a renal limitation in phosphate excretion. The 1- to 2-week-old puppy adjusts renal reabsorption of phosphate to maintain a concentration of phosphate in plasma higher than in the adult animal. The renal alterations in response to variations in dietary phosphate occur independently of plasma phosphate concentration, GFR, or filtered load of phosphate.

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