Plasma and bronchoalveolar fluid concentrations of nitric oxide and localization of nitric oxide synthesis in the lungs of horses with summer pasture-associated obstructive pulmonary disease.

This research aims to identify how nitric oxide behaves in the plasma and bronchoalveolar fluid of horses suffering from summer pasture-associated obstructive pulmonary disease. The study suggests that nitric oxide could potentially amplify inflammatory processes within the airways of afflicted horses.

Research Methodology

The study involved two groups of adult horses, one group of seven horses diagnosed with summer pasture-associated obstructive pulmonary disease (SPAOPD) and a control group of six clinically normal horses.

• The severity of the SPAOPD was assessed using clinical scores, changes in intrapleural pressure during tidal breathing, bronchoalveolar lavage fluid (BALF) cytologic analysis, and histologic examination of lung specimens obtained postmortem.
• Chemiluminescent methods were used to determine nitric oxide concentrations in plasma, BALF, and epithelial lining fluid (ELF).
• Immunohistochemical staining was performed on formalin-fixed lung specimens to localize inducible nitric oxide synthase (iNOS) and nitrotyrosine (NT), proteins associated with nitric oxide production.
• Using histochemical staining, researchers localized nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) activity in frozen specimens. NADPHd is an important enzyme in nitric oxide synthesis.

Research Findings

The findings of the research showed that while nitric oxide concentration in the plasma of SPAOPD affected horses was slightly higher, the difference was not statistically significant when compared to the nonaffected horses. Moreover, there was no difference in nitric oxide concentrations in BALF or ELF between the two groups.

• The study found increased expression of iNOS in bronchial epithelial cells in SPAOPD afflicted horses when compared to the control group. This suggests an amplified production of nitric oxide in SPAOPD affected horses.
• However, the staining for NT and NADPHd activity, other markers of nitric oxide production, did not differ between SPAOPD and control horses.

Conclusions

While there were no significant differences in nitric oxide concentrations between SPAOPD affected and nonaffected horses, the study showed an increased expression of iNOS in the bronchial epithelial cells of SPAOPD horses. This suggests that nitric oxide may potentially play a role in the intensification of the inflammatory process in SPAOPD afflicted horses’ airways. Further research is needed to confirm the exact role of nitric oxide in the disease process and whether nitric oxide synthesis inhibiting treatments may be of value in managing this condition in horses.