Effect of exercise on erythrocyte beta-adrenergic receptors and plasma concentrations of catecholamines and thyroid hormones in Thoroughbred horses.
Abstract: The effects of exercise stress on erythrocyte beta-adrenergic receptor characteristics and plasma concentrations of adrenaline, noradrenaline and thyroid hormones were studied in Thoroughbred racehorses during rest and after exercise. Five minutes after a maximal speed race of 1200 +/- 200 m (mean +/- s.d.), both plasma adrenaline and noradrenaline concentrations increased with respect to basal values (from 2.48 +/- 0.15 to 3.83 +/- 0.27 and from 2.13 +/- 0.11 to 3.53 +/- 0.27 nmol/l respectively). The increment of adrenaline was greater in high performance (HP) as compared to low performance (LP) horses (76.9 vs. 43.5%), in accordance with the contribution of the adrenal medulla in the sympathoadrenal response to exercise. Triiodothyronine (T3), but not thyroxine (T4) levels increased 5 min after exercise (from 55.6 +/- 2.9 to 81 +/- 3.7 ng/dl and from 0.67 +/- 0.04 to 0.70 +/- 0.05 micrograms/dl respectively). No differences were observed in basal values of thyroid hormones or in the percentage of T3 increment, when comparing HP vs. LP horses. Erythrocyte membranes obtained 5 min after racing showed decreased concentrations of beta-adrenergic receptors (beta-AR) and dissociation constant as compared to basal values (50.1 +/- 7.0 vs. 95.7 +/- 12.0 fmol/mg protein and 0.97 +/- 0.24 vs. 2.04 +/- 0.3 nmol/l respectively). This temporal pattern suggest that the observed changes in beta-AR characteristics could be mediated by catecholamines, but not by thyroid hormones, in this model. This down regulation of beta-AR may act as a protecting mechanism preventing the erythrocytes from the decrease in membrane fluidity known to be provoked by adrenergic agonists. The accomplished study showed that, in the Thoroughbred horse, there is a homeostatic response to race stress, characterised by a sudden increase in plasma catecholamines and T3 and a parallel decrease in beta-AR concentration on the erythrocyte membrane. In this way the racing horse could rapidly adjust its metabolism to the exercise stress, but at the same time override one possible undesirable side-effect caused by these hormonal changes. Further studies will be required to establish performance-related differences occurring in endocrine changes.
Publication Date: 1998-02-12 PubMed ID: 9458402DOI: 10.1111/j.2042-3306.1998.tb04091.xGoogle Scholar: Lookup
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Summary
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This study investigates how strenuous exercise affects hormone levels and erythrocyte beta-adrenergic receptor characteristics in Thoroughbred racehorses, with observed changes suggesting a protective mechanism to facilitate quick metabolic adjustments and minimize harmful side-effects.
Overview of the Study
- This research exercise aims to understand the effects of strenuous physical activity on the hormone levels and erythrocyte beta-adrenergic receptors in Thoroughbred racing horses.
- The study measured changes in hormone levels and erythrocyte beta-adrenergic receptor characteristics during rest and after intense exercise.
Effects of Exercise on Hormone Levels
- The procedure subjected horses to a maximum speed race, followed by a measurement of adrenaline and noradrenaline levels 5 minutes after completion. The exercise resulted in an increase in both adrenaline and noradrenaline levels.
- The spike in adrenaline levels was found to be more significant in high-performing horses as compared to lower-performing animals.
- Furthermore, levels of triiodothyronine (T3) hormones also increased after the race, while thyroxine (T4) levels remained stable.
- The above data suggests an integral role of adrenal medulla in adrenal stress response to exercise, especially in high-performing horses.
- Notably, there were no significant differences when comparing the base values of thyroid hormones or percentage increment of T3 in high-performing versus low-performing horses.
Effects on Erythrocyte’s Beta-adrenergic Receptors
- In addition to hormonal changes, the study observed that exercised horses demonstrated reduced concentrations of erythrocyte’s beta-adrenergic receptors (beta-AR) and dissociation constant relative to rest state values.
- These patterns suggest that these changes in beta-AR could be instigated by catecholamines, but not thyroid hormones.
- This diminution of beta-AR is thought to act as a protection mechanism by preventing the erythrocyte membranes from reduction in fluidity, a side effect of adrenergic agonists.
Conclusion and Further Research
- The study concluded that Thoroughbreds manifest a homeostatic response under racing stress. This is characterized by a swift increase in plasma catecholamines and T3, alongside a simultaneous decrease in beta-AR concentration on erythrocyte membrane.
- Such changes enable the horse to rapidly adjust its metabolism to exercise stress while reducing any potential detrimental effects caused by these hormonal fluctuations.
- However, the research suggests that further studies are necessary to elucidate endocrine changes that may occur in relation to performance.
Cite This Article
APA
González O, González E, Sánchez C, Pinto J, González I, Enríquez O, Martínez R, Filgueira G, White A.
(1998).
Effect of exercise on erythrocyte beta-adrenergic receptors and plasma concentrations of catecholamines and thyroid hormones in Thoroughbred horses.
Equine Vet J, 30(1), 72-78.
https://doi.org/10.1111/j.2042-3306.1998.tb04091.x Publication
Researcher Affiliations
- Department of Physiology and Biophysics, Faculty of Medicine, University of Chile, Santiago, Chile.
MeSH Terms
- Animals
- Catecholamines / blood
- Down-Regulation
- Epinephrine / blood
- Erythrocytes / chemistry
- Erythrocytes / metabolism
- Female
- Horses / blood
- Horses / metabolism
- Horses / physiology
- Male
- Norepinephrine / blood
- Physical Conditioning, Animal / physiology
- Receptors, Adrenergic, beta / analysis
- Receptors, Adrenergic, beta / metabolism
- Receptors, Adrenergic, beta / physiology
- Rest / physiology
- Thyroid Hormones / blood
- Thyroxine / blood
- Time Factors
- Triiodothyronine / blood
Citations
This article has been cited 5 times.- Giers J, Bartel A, Kirsch K, Müller SF, Horstmann S, Gehlen H. Blood-based assessment of oxidative stress, inflammation, endocrine and metabolic adaptations in eventing horses accounting for plasma volume shift after exercise. Vet Med Sci 2024 May;10(3):e1409.
- Henshall C, Randle H, Francis N, Freire R. The effect of stress and exercise on the learning performance of horses. Sci Rep 2022 Feb 4;12(1):1918.
- Papadopoulos C, Tentes I, Anagnostopoulos K. Molecular Interactions between Erythrocytes and the Endocrine System. Maedica (Bucur) 2021 Sep;16(3):489-492.
- Ferlazzo A, Cravana C, Fazio E, Medica P. The different hormonal system during exercise stress coping in horses. Vet World 2020 May;13(5):847-859.
- Sp N, Kang DY, Kim DH, Lee HG, Park YM, Kim IH, Lee HK, Cho BW, Jang KJ, Yang YM. Methylsulfonylmethane inhibits cortisol-induced stress through p53-mediated SDHA/HPRT1 expression in racehorse skeletal muscle cells: A primary step against exercise stress. Exp Ther Med 2020 Jan;19(1):214-222.
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