Plasma and pulmonary fluid endothelin in horses with seasonal recurrent airway obstruction.
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.


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


METHODS
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
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.
Costa
L R R
LR
Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, LA, USA. lais.costa@tufts.edu
Eades
S C
SC
Venugopal
C S
CS
Moore
R M
RM
D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry*; D016232:Endothelins / Q000032:analysis*; D005260:Female; D006734:Horse Diseases / Q000097:blood*; D006736:Horses; D008173:Lung Diseases, Obstructive / Q000097:blood / Q000378:metabolism / Q000662:veterinary*; D008297:Male; D011446:Prospective Studies; D012129:Respiratory Function Tests; D012621:Seasons; D013997:Time Factors
D016232:Endothelins