The kinetics of inorganic phosphate excretion in the acidotic rabbit during intravenous phosphate loading.pdf (1.23 MB)

The kinetics of inorganic phosphate excretion in the acidotic rabbit during intravenous phosphate loading: a pseudo-ruminant model.

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posted on 08.02.2021, 18:04 by Patrick A Walsh, Daniel J O'Donovan
The rabbit is a much-used experimental animal in renal tubule physiology studies. Although a monogastric mammal, the rabbit is a known hindgut fermenter. That ruminant species excrete inorganic phosphate (Pi) mainly through the digestive system while non-ruminants eliminate surplus phosphate primarily through the renal system are acknowledged facts. To understand phosphate homeostasis in the acidotic rabbit, anaesthetized animals were infused with hydrochloric acid, after which they underwent intravenous phosphate loading. Biofluids were collected during the infusion process for analysis. Plasma Pi increased (7.9 ± 1.7 mmoles.Litre-1 (N = 5) vs 2.2 ± 0.4 mmoles.Litre-1 (N = 10) pre-infusion, (p < 0.001)), while urinary phosphate excretion was also enhanced (74.4 ± 15.3 from a control value of 4.7 ± 3 µmol.min-1 (N = 9), pre-infusion, p < 0.001)) over an 82.5 minute Pi loading period. However, the fractional excretion of Pi (FePi) only increased from 14.2 ± 5.4% to a maximum of 61.7 ± 19% (N = 5) over the infusion period. Furthermore, the renal tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmPi/GFR) computed to 3.5 mmol.L-1, while a reading of 23.2 µmol.min-1.Kg.0.75 was obtained for the transport maximum for Pi (TmPi). The high reabsorptivity of the rabbit nephrons coupled with possibly a high secretory capacity of the salivary glands for Pi, may constitute a unique physiological mechanism that ensures the rabbit hindgut receives adequate phosphate to regulate caecal pH in favour of the resident metabolically - active microbiota. The handling of Pi by the rabbit is in keeping with the description of this animal as a monogastric, pseudo-ruminant herbivore.

Funding

Medical Research Council of Ireland

National University of Ireland Galway (Postgraduate Fellowship).

Department of Education, Ireland

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The original article is available at https://www.nature.com/

Published Citation

Walsh PA, O'Donovan DJ. The kinetics of inorganic phosphate excretion in the acidotic rabbit during intravenous phosphate loading: a pseudo-ruminant model. Scientific Reports. 2020;10(1):3988.

Publication Date

4 March 2020

PubMed ID

32132645

Department/Unit

  • RCSI Bahrain

Publisher

Springer Nature Limited

Version

  • Published Version (Version of Record)

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Exports

Royal College of Surgeons in Ireland

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