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Paradoxical response to parathyroid hormone of renal handling of phosphate in hyperparathyroid rats.

Authors
  • Kimura, S
  • Yamamoto, M
  • Itakura, M
  • Koide, Y
  • Kugai, N
  • Abe, K
  • Ogata, E
Type
Published Article
Journal
Endocrinology
Publication Date
Nov 01, 1982
Volume
111
Issue
5
Pages
1666–1670
Identifiers
PMID: 6290192
Source
Medline
License
Unknown

Abstract

The effect of PTH given as a bolus on renal handling of phosphate in rats was studied by a perfusion balance study method. In vitamin D-fed rats, iv PTH as a bolus (10 USP units) elicited a phosphaturic response and an increase in urinary cAMP, whether or not the rats were thyroparathyroidectomized. When given to thyroparathyroidectomized rats receiving continuous infusion of PTH (2.5 USP units/h) for 16 h, PTH led to a paradoxical decline of phosphate clearance in spite of an increase in urinary cAMP. Vitamin D-deficient intact rats also showed this paradoxical response. Vitamin D-deficient thyroparathyroidectomized rats showed an ordinary phosphaturic response. When PTH had been supplied continuously (2.5 USP units/h) to these rats, the PTH bolus again produced the paradoxical response. Phosphate supplementation did not restore the phosphaturic response. (Bu)2cAMP infusion reproduced the paradoxical effect in vitamin D-fed, thyroparathyroidectomized rats receiving continuous infusion of PTH. These data indicate that a long-lasting excess of circulating PTH alters the nature of the response of the kidney to an iv bolus of PTH, so that PTH leads to a paradoxical decline of phosphate clearance, and that the mechanism responsible for the paradox may lie in a step (or steps) subsequent to cAMP production.

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