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Urinary Cortisol excretion in the resting and exercising horse
Author(s) -
TOUTAIN P. L.,
LASSOURD V.,
POPOT M. A.,
LAROUTE V.,
ALVINERIE M.,
BONNAIRE Y.
Publication year - 1995
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.1995.tb04973.x
Subject(s) - urine , horse , medicine , endocrinology , hydrocortisone , bolus (digestion) , crossover study , urinary system , chemistry , biology , paleontology , alternative medicine , pathology , placebo
Summary The aim of this study was to document the 24 h urinary Cortisol concentrations during a rest day and a day that included prolonged exercise. The influence of exercise on disposition (plasma, urine) of a dose of Cortisol (1 mg/kg) was also assessed. Six adult saddle horses were used. In one experiment, urinary Cortisol elimination rates were measured during rest and prolonged exercise (56 km, 12 km/h) corresponding to about 50% of the V̇O 2max . In another experiment, horses received, according to a crossover design, an intravenous (i.v.) bolus administration of Cortisol (1 mg/kg) either at rest or during the same prolonged exercise. The urine Cortisol concentration was lower than 100 ng/ml in the control resting horse. It was increased by exercise but the maximal concentration was lower than 300 ng/ml and returned to control values by 10 h after the end of exercise. After 1 mg/kg Cortisol i.v. Cortisol clearance was decreased by exercise (552 ± 143 vs. 452 ± 59 ml/kg/h, mean ± s.d.), but the difference was not significant The peaks of urinary Cortisol ranged from 760 to 21,967 ng/ml and occurred 0.8 to 6.9 h after Cortisol administration depending on the time of the first urination after administration. The return to values below 100 ng/ml was observed after 21 h in all horses. The 1000 ng/ml threshold for Cortisol control in urine after i.v. Cortisol (1 mg/kg) is specific (conservative) but of low sensitivity.