Immunohistochemical determination of the expression of endothelin receptors in bronchial smooth muscle and epithelium of healthy horses and horses affected by summer pasture-associated obstructive pulmonary disease.
OBJECTIVE
To immunohistochemically determine the expression of endothelin (ET) receptors in bronchial smooth muscle and epithelium of healthy horses and horses affected by summer pasture-associated obstructive pulmonary disease (SPAOPD).


METHODS
Tissue specimens obtained from 8 healthy and 8 SPAOPD-affected horses.


METHODS
Horses were examined and assigned to healthy and SPAOPD groups. Horses were then euthanatized, and tissue specimens containing bronchi of approximately 4 to 8 mm in diameter were immediately collected from all lung lobes, fixed in zinc-formalin solution for 12 hours, and embedded in paraffin. Polyclonal primary antibodies against ET-A or ET-B receptors at a dilution of 1:200 and biotinylated IgG secondary antibodies were applied to tissue sections, followed by the addition of an avidin-biotin immunoperoxidase complex. Photographs of the stained slides were digitally recorded and analyzed by use of image analysis software to determine the intensity of staining. Two-way ANOVA was used for statistical analysis.


RESULTS
The left diaphragmatic lung lobe of SPAOPD-affected horses had a significantly greater area of bronchial smooth muscle that immunostained for ET-A, compared with that for healthy horses. All lung lobes of SPAOPD-affected horses, except for the right diaphragmatic lobe, had significantly greater staining for ET-B receptors in bronchial smooth muscle, compared with results for healthy horses.


CONCLUSIONS
This study revealed overexpression of ET-A and, in particular, ETB receptors in the bronchial smooth muscle of SPAOPD-affected horses, which suggested upregulation of these receptors. These findings improve our understanding of the role of ET-1 in the pathogenesis of SPAOPD.
Polikepahad
Sumanth
S
Equine Health Studies Program, Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
Paulsen
Daniel B
DB
Moore
Rustin M
RM
Costa
Lais R R
LR
Venugopal
Changaram S
CS
D000818:Animals; D016022:Case-Control Studies; D004848:Epithelium / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D006262:Health; D006734:Horse Diseases / Q000378:metabolism*; D006736:Horses / Q000378:metabolism*; D007150:Immunohistochemistry; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008173:Lung Diseases, Obstructive / Q000378:metabolism / Q000662:veterinary*; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism*; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism*; D012621:Seasons
D017466:Receptors, Endothelin