Endothelin response during and after exercise in horses.
Authors: McKeever Kenneth H, Antas Lisa A, Kearns Charles F
Journal: Veterinary journal (London, England : 1997)
Summary
# Endothelin Response During and After Exercise in Horses Endothelin-1 (ET-1), a potent vasoconstrictor involved in vascular regulation and oxygen delivery, has not been extensively characterised during equine exercise, prompting McKeever and colleagues to measure plasma ET-1 responses across different exercise intensities. Six unfit but treadmill-accustomed mares underwent three protocols: resting baseline measurements, a graded incremental exercise test to fatigue, and 15 minutes of submaximal steady-state exercise at 60% VO₂max, with plasma sampling via jugular venepuncture at strategic intervals throughout each trial. Resting ET-1 concentrations averaged 0.18 pg/mL and remained unchanged during incremental exercise (0.20 pg/mL average), yet rose significantly immediately post-exercise and at the 2-minute recovery mark following submaximal work, normalising by 10 minutes of recovery. This biphasic response—absent during dynamic exertion but elevated post-exercise—suggests ET-1 secretion may be triggered by the metabolic or haemodynamic perturbations of recovery rather than the exercise stimulus itself, potentially serving a regulatory role in stabilising vascular function during the post-exercise transition. For practitioners managing horses in training, this indicates that vascular adaptations continue beyond the cessation of work; understanding ET-1 dynamics could inform recovery protocols and inform assessment of abnormal cardiovascular responses to routine exercise.
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Practical Takeaways
- •Endothelin-1 elevation occurs after submaximal exercise, suggesting it may play a role in post-exercise vascular and metabolic responses in horses
- •ET-1 normalization within 10 minutes of recovery indicates rapid physiological adaptation, which may be relevant when planning recovery protocols
- •Different exercise intensities and types produce different ET-1 responses, suggesting endothelin's role is specifically related to sustained steady-state work rather than interval training
Key Findings
- •Plasma endothelin-1 (ET-1) concentrations remained stable at 0.18±0.03 pg/mL during standing control and did not change during graded exercise testing
- •ET-1 concentrations were significantly elevated immediately post-exercise and at 2 minutes post-exercise during 15-minute submaximal (60% VO₂max) steady-state exercise
- •Post-exercise ET-1 concentrations returned to baseline by 10 minutes of recovery
- •ET-1 response appears specific to submaximal steady-state exercise rather than progressive incremental exercise intensity