Document Detail

Plasma cortisol and beta-endorphin concentrations in trained and over-trained standardbred racehorses.
MedLine Citation:
PMID:  10650995     Owner:  NLM     Status:  MEDLINE    
The effects of training and over-training on plasma cortisol and beta-endorphin (betaEP) concentrations at rest and after standardised exercise tests and the cortisol responses to adrenocorticotropin (ACTH) administration were investigated in standardbred horses. Twelve horses were divided randomly into control and over-trained (OT) groups after 17 weeks slow- and moderate-intensity treadmill training. The standardised treadmill exercise test consisted of 2 min at velocities corresponding to 30, 50, 70 and 100% of maximum O2 consumption. Over-training, defined as a significant decrease in body weight and treadmill run-time-to-fatigue in an incremental velocity test, occurred in the OT group after 32 weeks of training exercise. Peak cortisol concentrations after exercise decreased significantly in the OT group from 320+/-15.6 at week 8 to 245+/-17.0 nmol l(-1) at week 32, and mean cortisol concentrations over a 120-min period after exercise decreased from 258+/-11.7 to 192+/-16.6 nmol l(-1) (P<0.05). Mean and total cortisol and betaEP concentrations in resting horses were not significantly different after over-training. Peak cortisol concentrations after adrenocorticotropin (ACTH) administration were not significantly different in the over-trained group. Dysfunction of the hypothalamo-pituitary-adrenocortical axis occurs in over-trained horses, but this adaptation is not associated with a change in the adrenocortical responsiveness to ACTH.
L C Golland; D L Evans; G M Stone; C M Tyler-McGowan; D R Hodgson; R J Rose
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Pflügers Archiv : European journal of physiology     Volume:  439     ISSN:  0031-6768     ISO Abbreviation:  Pflugers Arch.     Publication Date:  1999 Dec 
Date Detail:
Created Date:  2000-03-02     Completed Date:  2000-03-02     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0154720     Medline TA:  Pflugers Arch     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  11-7     Citation Subset:  IM    
Department of Animal Science, University of Sydney, NSW, Australia.
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MeSH Terms
Adrenal Glands / drug effects,  physiology
Adrenocorticotropic Hormone / pharmacology
Exercise Test
Horses / physiology*
Hydrocortisone / blood*
Physical Conditioning, Animal / physiology*
Time Factors
beta-Endorphin / blood*
Reg. No./Substance:
50-23-7/Hydrocortisone; 60617-12-1/beta-Endorphin; 9002-60-2/Adrenocorticotropic Hormone

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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