Doctor of Philosophy (PhD)


Biomedical and Veterinary Medical Sciences - Comparative Biomedical Sciences

Document Type



Endothelin-1 (ET-1) has been implicated in allergic type of respiratory inflammatory diseases in various species of animals including horses. This peptide elicits its actions by acting through endothelin-A (ET-A) and endothelin-B (ET-B) receptor sub-types. In this project, we have hypothesized that endothelin receptors (both ET-A and ET-B) are altered in terms of affinity and expression, in the lungs of summer pasture-associated obstructive pulmonary disease (SPAOPD)-affected horses. Objective of this dissertation was to determine the alterations in the affinity and expression of endothelin receptors in the lungs of healthy and SPAOPD-affected horses. To pursue our hypothesis, we have employed pharmacological, immunohistochemical and molecular studies. Totally 33 horses were used in this study. All the horses were examined and grouped in to 16 healthy and 17 SPAOPD-affected, based on clinical evaluation, clinical scoring, pulmonary function testing and broncho-alveolar lavage fluid (BALF) analysis. Horses were then euthanatized, and tissue specimens were immediately collected from all lung lobes. In pharmacological studies, cumulative concentration response curves and pA2 values were determined and compared in both groups of horses. The pA2 value of ET-B receptors was significantly greater in the SPAOPD-affected horses when compared with healthy horses. In immunohistochemical studies, expression of these receptors was determined in the bronchial smooth muscles and epithelium of both groups of horses. The percentage of immunostaining was significantly greater in the smooth muscles of SPAOPD-affected horses when compared with healthy horses. In molecular studies, by employing RT-PCR, western blotting and realtime PCR, expression of these receptors has been determined and compared. The molecular expression of ET-B receptors was siginifcantly greater in the peripheral lungs of SPAOPD-affected horses when compared with healthy horses. Specific antagonists, primers and polyclonal primary antibodies of ET-A or ET-B receptors were used for these three studies. On the whole, it can be concluded that ET-B receptors show a clear tendency of up-regulation in the lungs of SPAOPD-affected horses. These findings help us in the better understanding of the pathogenesis of this progressive, career-ending disease.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Changaram S. Venugopal