Comparative responses of bronchial rings to mediators of airway hyperreactivity in healthy horses and those affected with summer pasture-associated obstructive pulmonary disease.

This study explores how bronchial rings from healthy horses and horses afflicted with summer pasture-associated obstructive pulmonary disease (SPAOPD) respond to different mediators of airway hyperreactivity in laboratory conditions.

Research Methodology

• The study used bronchial rings from six healthy horses and six horses afflicted with SPAOPD.
• These bronchial rings were placed in organ baths and attached to force transducers that were linked with a polygraph.
• After applying a 2g tension, each ring was allowed to stabilize for 45 minutes in Tyrode’s solution at 37 C.
• The respective concentration-response relationships to progressing concentrations of selected mediators were determined and analyzed for significance at each concentration.

Experimental Results

• Certain mediators – acetylcholine, histamine, 5-hydroxytryptamine, and leukotriene D4 – induced concentration-dependent contractile responses in bronchial rings.
• Prostaglandin F2alpha resulted in weak and irregular contractile responses.
• The other two agents, norepinephrine and substance P, failed to induce concentration-dependent responses.
• Four mediators (acetylcholine, histamine, 5-hydroxytryptamine, and leukotriene D4) were effective in triggering reliable concentration-dependent contractile responses in both groups.
• Only 5-hydroxytryptamine and histamine induced significant responses in contractility between the two groups of horses used in the study.

Significant Findings and Conclusion

• Bronchial rings from horses with SPAOPD showed a significantly higher response to 5-hydroxytryptamine compared to those from healthy horses. Conversely, their response to histamine was significantly lower.
• These significant responses were observed at concentrations ranging from 10^(-6) to 10^(-4) M for both drugs.
• The researchers concluded that since the airways of horses with SPAOPD demonstrated increased responsiveness to 5-hydroxytryptamine under lab conditions, the potential use of drugs that counteract 5-hydroxytryptamine should be investigated as a possible treatment option.