Cortisol disposition and production rate in horses during rest and exercise.
The influence of a 56-km endurance exercise on cortisol kinetics and production rate was evaluated in six horses administered [3H]cortisol. Exercise resulted in an immediate two- to threefold increase in plasma cortisol, with values returning very rapidly to preexercise levels. During exercise, clearance and steady-state volume of distribution of total cortisol were greatly increased (338 +/- 95 vs. 137 +/- 34 ml.kg-1.h-1 for clearance and 359 +/- 82 vs. 229 +/- 18 ml/kg for volume of distribution), whereas the terminal half-life decreased significantly (0.97 +/- 0.16 vs. 1.55 +/- 0.33 h). The estimated cortisol production rate was 4.41 +/- 1.06 micrograms.kg-1.h-1 at rest and 26.75 +/- 5.11 micrograms.kg-1.h-1 during exercise. We conclude that exercise triggers a large increase (x 6) in the adrenal secretion rate, which is not accurately reflected by the more limited increase (x 2-3) in plasma cortisol concentration, the actual measurement of plasma cortisol clearance being a prerequisite to assessment of adrenal gland function during exercise.
Lassourd
V
V
Ecole Nationale Vétérinaire de Toulouse, Département de Physiopathologie, France.
Gayrard
V
V
Laroute
V
V
Alvinerie
M
M
Benard
P
P
Courtot
D
D
Toutain
P L
PL
D000818:Animals; D006736:Horses / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood / Q000493:pharmacokinetics*; D008954:Models, Biological; D009994:Osmolar Concentration; D005082:Physical Exertion; D012146:Rest; D012709:Serum Albumin / Q000378:metabolism; D013997:Time Factors
D012709:Serum Albumin; D006854:Hydrocortisone