The role of cyclooxygenase products in the acute airway obstruction and airway hyperreactivity of ponies with heaves.

The research investigates the role of certain metabolites in the onset and development of heaves, a respiratory disorder similar to human asthma, in ponies. The results suggest that while these metabolites are changed during the disease state, they do not significantly impact the severity of airway obstruction or overreactions.

Background of the Research

• The study focuses on heaves, a respiratory disorder in horses and ponies that presents symptoms similar to human asthma, such as airway obstruction and overreaction.
• The researchers aimed to document the role of cyclooxygenase products originating from the metabolism of arachidonic acid, a fatty acid involved in the inflammation and immune response, in the development of heaves.
• Specifically, metabolites of thromboxane (TX)A2 and prostaglandins (PG)I2 and D2, which are involved in blood clotting and inflammation, respectively, are examined in the research.

Research Methodology

• The traits of the disease were compared in five ponies suffering from heaves and a control group of similar ponies, both before and during acute airway obstruction.
• The obstruction was stimulated by placing the ponies in a barn environment and exposing them to hay dust.
• Changes in pulmonary resistance, dynamic compliance, arterial oxygen tension, and plasma TXB2 levels were measured in the different stages of the disease.
• Furthermore, the ponies were subjected to histamine aerosol to verify airway hyperresponsiveness, another symptom of heaves.
• In a subsequent experiment, the ponies were treated with flunixin meglumine, a cyclooxygenase inhibitor, to check if this treatment would impact the onset or development of the disease.

Key Findings and Conclusion

• The results of the experiments show that during the acute disease state, plasma TXB2 is the only metabolite whose levels significantly increase.
• However, treating the ponies with a cyclooxygenase inhibitor, which prevented the production of TXB2, did not change the degree of airway obstruction or hyperreactivity.
• This led to the conclusion that although metabolite levels change during the progression of heaves, they do not directly influence the severity of the symptoms.