Hysteresis and calcium set-point for the calcium parathyroid hormone relationship in healthy horses.
Abstract: Abnormalities in calcium (Ca(2+)) homeostasis are reported in horses with several pathological conditions; however, there is little information on Ca(2+) regulation in horses. The objectives of the present study were to determine the Ca(2+) set-point in healthy horses, to determine whether the Ca(2+)/parathyroid hormone (PTH) response curves were characterized by hysteresis, and to determine if the order of experimentally induced hypocalcemia or hypercalcemia had an effect on PTH secretion. The Ca(2+) set-point and hysteresis were determined in 12 healthy horses by infusing Na(2)EDTA and calcium gluconate. The Ca(2+) set-point was 1.37 +/- 0.05 mmol/L, which is higher than values reported for humans and dogs (1.0-1.2 mmol/L). Hysteresis was present during hypocalcemia and hypercalcemia. Horses in which hypocalcemia was followed by hypercalcemia secreted more PTH (7440 +/- 740 pmol min/L) than horses in which hypercalcemia was followed by hypocalcemia (5990 +/- 570 pmol min/L). This study has demonstrated that the Ca(2+) set-point in the horse is higher than in other domestic animals and man. We have shown that the Ca(2+)/PTH relationship in horses is sigmoidal and displays hysteresis during both hypocalcemia and hypercalcemia, and that extracellular Ca(2+) concentrations may affect the response of the parathyroid gland to hypocalcemia.
Copyright 2003 Elsevier Science (USA)
Publication Date: 2003-02-28 PubMed ID: 12606270DOI: 10.1016/s0016-6480(02)00621-4Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research investigates how the calcium-parathyroid hormone relationship functions in healthy horses, including identifying the calcium set-point and analysing patterns involving calcium level shifts like hysteresis. The study highlights that the calcium set-point is higher in horses than in humans and dogs and that hysteresis occurs in cases of both low and high calcium levels.
Objectives and Methodology
- This study aimed primarily to identify the calcium set-point in healthy horses. It also aimed to analyse the calcium-parathyroid hormone (PTH) response curves for hysteresis (nonlinear patterns involving variations in calcium levels).
- The researchers wanted to understand whether the sequence of experimentally induced low calcium (hypocalcemia) or high calcium (hypercalcemia) levels affected the secretion of PTH.
- The study involved a sample of 12 healthy horses, and the researchers used sodium EDTA and calcium gluconate infusions for inducing variations in calcium levels.
Findings and Implications
- The calcium set-point found in this study was 1.37 +/- 0.05 mmol/L. This value is higher than those reported for humans and dogs, typical values for those species range between 1.0-1.2 mmol/L.
- Hysteresis was present in the calcium-PTH response curves both when calcium levels were unnaturally low (hypocalcemia) and high (hypercalcemia).
- A potentially significant finding was that the horses, subject to artificially induced hypocalcemia followed by hypercalcemia, secreted more PTH than the horses exposed to the reverse sequence. Specific secretion levels reported were 7440 +/- 740 pmol min/L and 5990 +/- 570 pmol min/L, respectively.
- This study contributes to a better understanding of how calcium homeostasis functions in horses, a subject not as extensively studied as in humans and other animals. The research demonstrates that the calcium set-point in horses is higher and provides initial insight into how fluctuations in calcium levels may affect PTH secretion.
Cite This Article
APA
Toribio RE, Kohn CW, Sams RA, Capen CC, Rosol TJ.
(2003).
Hysteresis and calcium set-point for the calcium parathyroid hormone relationship in healthy horses.
Gen Comp Endocrinol, 130(3), 279-288.
https://doi.org/10.1016/s0016-6480(02)00621-4 Publication
Researcher Affiliations
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA. toribio.1@osu.edu
MeSH Terms
- Analysis of Variance
- Animals
- Area Under Curve
- Calcium / blood
- Calcium / pharmacokinetics
- Female
- Homeostasis / physiology
- Horses / blood
- Hypercalcemia / blood
- Hypercalcemia / veterinary
- Hypocalcemia / blood
- Hypocalcemia / veterinary
- Male
- Parathyroid Hormone / blood
- Parathyroid Hormone / metabolism
- Reference Values
- Time Factors
Citations
This article has been cited 4 times.- Fradinho MJ, Mateus L, Bernardes N, Bessa RJB, Caldeira RM, Ferreira-Dias G. Growth patterns, metabolic indicators and osteoarticular status in the Lusitano horse: A longitudinal study.. PLoS One 2019;14(7):e0219900.
- Pruett WA, Hester RL, Coleman TG. The apparent hysteresis in hormone-agonist relationships.. J Theor Biol 2012 Mar 7;296:1-5.
- Keenan DM, Iranmanesh A, Veldhuis JD. Analytical construct of reversible desensitization of pituitary-testicular signaling: illustrative application in aging.. Am J Physiol Regul Integr Comp Physiol 2011 Feb;300(2):R349-60.
- Brown EM. Calcium sensing by endocrine cells.. Endocr Pathol 2004 Fall;15(3):187-219.
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