Pediatric Nephrology

, Volume 4, Issue 4, pp 387–391 | Cite as

Regulation of renal phosphate reabsorption during development: implications from a new model of growth hormone deficiency

  • Aviad Haramati
  • Susan E. Mulroney
  • Michael D. Lumpkin
Proceedings of the Fourth International Workshop on Developmental Renal Physiology August 24–26, 1989 Montreal, Canada Review Article

Abstract

It has been hypothesized that the high rate of renal phosphate (Pi) reabsorption in the immature animal is a consequence of the increased demand for Pi associated with the rapid rate of growth. Although growth hormone (GH) has been proposed to play a role in this process, investigations of the relationship between GH, growth and the renal Pi transport have been hampered by the lack of methods available to specifically alter circulating GH levels. This review summarizes the findings from recent studies using a newly developed peptidic antagonist to GH-releasing factor (GRF-AN) as a method of specifically inhibiting GH release. Systemic injection of GRF-AN was effective in suppressing the pulsatile release of GH, and in significantly attenuating the rate of growth, in both immature and adult rats. However, the inhibition of growth was associated with a reduction in net Pi retention only in immature rats, resulting in a doubling in the urinary excretion of Pi. GRF-AN treatment of immature rats lead to a decrease in the maximum tubular capacity to transport Pi-down to the level seen in adult rats. However, GRF-AN treatment did not alter renal Pi reabsorption in adult rats. We conclude that chronic administration of an antagonist to GRF in rats provides a new model of GH deficiency with which to study the interrelationships between growth, GH and other physiological systems. Furthermore, the findings suggest that the pulsatile release of GH, directly or indirectly, contributes to the high rate of renal Pi reabsorption in young, growing animals and may play a critical role in regulating Pi homeostasis during development.

Key words

Renal phosphate reabsorption Growth hormone deficiency Growth hormone releasing factor antagonist Renal development Rat 

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Copyright information

© IPNA 1990

Authors and Affiliations

  • Aviad Haramati
    • 1
  • Susan E. Mulroney
    • 1
  • Michael D. Lumpkin
    • 1
  1. 1.Department of Physiology and BiophysicsGeorgetwon University School of MedicineWashington, DCUSA

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