• Open Access

Plasma and Pulmonary Fluid Endothelin in Horses with Seasonal Recurrent Airway Obstruction

Authors

  • L.R.R. Costa,

    1. From the Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University
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  • S.C. Eades,

    1. From the Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University
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  • C.S. Venugopal,

    1. From the Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University
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  • R.M. Moore

    1. From the Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University
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  • Dr Costa is presently affiliated with Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA. Dr Moore is presently affiliated with Department of Veterinary Clinical Sciences College of Veterinary Medicine, The Ohio State University, Columbus, OH. A portion of the data was presented in abstract form at the 2003 International Veterinary Emergency and Critical Care Symposium.

Corresponding author: Lais R.R. Costa, MV, MS, PhD, DACVIM, DABVP, 200 Westboro Road, North Grafton, MA 01536-1895; e-mail: lais.costa@tufts.edu.

Abstract

Background: Summer pasture-associated recurrent airway obstruction (SPA-RAO), a seasonal airway obstructive disease of horses, is characterized by clinical exacerbation after exposure to pasture during warm months of the year. Endothelin (ET)-1, potent bronchoconstrictor, mitogen, secretagogue, and proinflammatory mediator, has been implicated in the pathogenesis of asthma and equine heaves.

Hypothesis: Immunoreactive ET-1 concentrations increase during clinical exacerbation and return to basal values during periods of disease remission.

Animals: Twelve horses, 6 affected with SPA-RAO and 6 nonaffected.

Methods: Prospective, observational study. Bronchoalveolar lavage fluid (BALF), arterial and venous plasma samples, and clinical variables were obtained from affected horses during clinical exacerbation and remission. Samples and data of nonaffected horses were collected during the summer and winter on dates similar to affected horses. Immunoreactive ET-1 was determined using a commercial ELISA.

Results: The median and range ET-1 concentrations (pg/ml) in arterial (1.3, 0.7–1.8) and venous (1.3, 1.2–1.7) plasma and in BALF (0.3, 0.2–0.4), and pulmonary epithelial lining fluid (PELF) (25.5, 21–50) were greater in affected horses during clinical exacerbation compared with remission (P < .01). The concentrations of immunoreactive ET-1 were greater in affected horses during clinical exacerbation compared with nonaffected horses (P < .05).

Conclusions and Clinical Importance: During clinical exacerbation of SPA-RAO, ET-1 is increased in circulation and pulmonary secretions. Intervention with ET receptor antagonists should provide further information on the role of ET-1 in SPA-RAO.

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