Detection of endogenous cortisol in equine tears and blood at rest and after simulated stress.
Abstract: To determine whether cortisol is present in equine tears at rest and during simulated stress and compare tear cortisol to serum free and total cortisol. Methods: Fourteen healthy adult horses were included. Paired tear total cortisol and serum total and free cortisol concentrations were measured with ELISA, chemiluminescent immunoassay, and ultrafiltration methodology, respectively, in 10 horses at rest once daily for five consecutive days. In an additional four horses, paired tear and serum samples were collected for cortisol measurement before and after adrenocorticotropic hormone (ACTH) stimulation (cosyntropin, 1 μg/kg IV). Results: Cortisol was detectable in equine tears at rest. Following ACTH stimulation, tear cortisol increased significantly from baseline at 60-120 min (P ≤ 0.001). Serum total and free cortisol also increased significantly at 30-180 min after ACTH stimulation (P ≤ 0.001). Both serum and tear cortisol returned to baseline concentrations by 360 min. Changes in tear cortisol were similarly associated with changes in serum total and free cortisol, although high tear cortisol concentrations suggest a portion of tear cortisol may be protein-bound. Conclusions: Cortisol is present in equine tears and increases in concert with serum cortisol following ACTH stimulation. Further study is needed to determine whether endogenous cortisol in tears contributes to ocular pathology.
© 2013 American College of Veterinary Ophthalmologists.
Publication Date: 2013-12-13 PubMed ID: 24329958DOI: 10.1111/vop.12128Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research investigates the presence of cortisol in horse tears both at rest and during simulated stress, and draws comparisons between cortisol levels in tears and blood serum.
Research Method
- The researchers studied a total of 14 healthy adult horses.
- Measurements of cortisol concentrations were obtained from both tear and serum samples. Techniques used in these measurements include enzyme-linked immunosorbent assay (ELISA), chemiluminescent immunoassay, and an ultrafiltration method designed for separating free from protein-bound cortisol.
- In 10 horses, these measurements were taken once daily for five consecutive days while the horses were at rest.
- For an additional four horses, measurements were taken before and after stimulation of the horses’ adrenocorticotropic hormone (ACTH) using cosyntropin, which is a synthetic version of ACTH. This was done to simulate a stressful situation for these horses and observe the cortisol response.
Research Results
- The research found that cortisol is indeed present in equine tears when the horse is at rest.
- Following stimulation of ACTH, the cortisol levels in tears and serum both saw a substantial increase. This increase was observed between 30 to 180 minutes after the ACTH stimulation.
- Both the tear and serum cortisol levels returned to their baseline after 360 minutes post-stimulation.
- It was also suggested that a portion of the tear cortisol could be protein-bound due to the high concentrations observed.
Conclusions
- The findings from the research conclusively showed that cortisol is present in horse tears and it increases significantly in a stressful situation, in pace with serum cortisol.
- The study suggests future research is needed to determine if this cortisol present in tears has any implications for ocular health in horses.
Cite This Article
APA
Monk CS, Hart KA, Berghaus RD, Norton NA, Moore PA, Myrna KE.
(2013).
Detection of endogenous cortisol in equine tears and blood at rest and after simulated stress.
Vet Ophthalmol, 17 Suppl 1, 53-60.
https://doi.org/10.1111/vop.12128 Publication
Researcher Affiliations
- College of Veterinary Medicine, University of Georgia, Athens, GA, 30602, USA.
MeSH Terms
- Animals
- Female
- Horse Diseases / physiopathology
- Horses / blood
- Horses / physiology
- Hydrocortisone / analysis
- Hydrocortisone / blood
- Hydrocortisone / physiology
- Male
- Stress, Psychological / physiopathology
- Tears / chemistry
Citations
This article has been cited 4 times.- Kastelic M, Gregurić Gračner G, Tomažič I, Kvapil P, Harej M, Dovč A. Comparison of Cortisol Concentrations in Different Matrices in Alpine Ibex (Capra ibex) at the Zoo. Animals (Basel) 2023 Aug 2;13(15).
- Kikuchi M, Nagata SI, Ishige T, Minamijima Y, Hirota KI, Tozaki T, Kakoi H, Kizaki K. Evaluation of the effect of glucocorticoid treatment on adrenocortical functions by monitoring endogenous hydrocortisone in horses. J Vet Med Sci 2023 Jun 13;85(6):647-652.
- Falomo ME, Del Re B, Rossi M, Giaretta E, Da Dalt L, Gabai G. Relationship between postpartum uterine involution and biomarkers of inflammation and oxidative stress in clinically healthy mares (Equus caballus). Heliyon 2020 Apr;6(4):e03691.
- Rachidi F, Wagner R, Fieseler H, Kaiser M, Müller H, Bittner-Schwerda L, Podpečan O, Mielenz N, Gottschalk J, Einspanier A, Möbius G, Starke A. Tears and saliva as alternative matrices for minimally invasive assessment of acute stress and pain in sheep. Front Vet Sci 2026;13:1719442.
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