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Effects of a specific endothelin‐1 A antagonist on exercise‐induced pulmonary haemorrhage (EIPH) in Thoroughbred horses
Author(s) -
PADILLA D. J.,
EPP T. S.,
McDONOUGH P.,
MARLIN D. J.,
ERICKSON H. H.,
POOLE D. C.
Publication year - 2006
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.2042-3306.2006.tb05539.x
Subject(s) - medicine , horse , bronchoalveolar lavage , antagonist , treadmill , anesthesia , cardiology , receptor , lung , paleontology , biology
Summary Reasons for performing study: During high intensity exercise, the very high pulmonary artery pressure (Ppa) experienced by Thoroughbred horses is considered a major factor in the aetiology of exercise‐induced pulmonary haemorrhage (EIPH). Recently, endothelin‐1 (ET‐1), a potent vasoconstrictive hormone, has been found to increase Ppa in horses at rest via binding to its ET‐1 A receptor subtype. In addition, plasma concentrations of ET‐1 are increased in horses during and after high intensity exercise. Hypothesis: If ET‐1 increases Ppa during exercise in the horse, administration of a specific ET‐1 A antagonist would decrease Ppa and therefore EIPH. Methods: Saline (CON) or an ET‐1 A receptor antagonist, TBC3214 (3 mg/kg bwt i.v.; ANTAG) was administered to horses 1 h prior to maximal incremental exercise on a highspeed treadmill. Gas exchange measurements were made breath‐by‐breath and blood samples collected during each 1 min stage to determine blood gases, acid‐base status and cardiac output. EIPH was determined via bronchoalveolar lavage (BAL) ˜30 min after exercise. Results: The time to fatigue, gas exchange and cardiovascular responses were not different between groups (P>0.05). Resting and peak Ppa did not differ significantly between treatments. Most importantly, ANTAG did not decrease EIPH. Conclusions: These results do not support a deterministic role for ET‐1 in the increased Ppa and therefore EIPH, during maximal exercise in the equine athlete. Potential relevance: Treatment with an ET‐1 A receptor antagonist does not appear to be a viable therapeutic intervention in the prevention of EIPH.