Surfactant alterations in horses with recurrent airway obstruction at various clinical stages.

The research aims to analyze the content and function of surfactant, a substance that reduces surface tension in the lungs, among horses with recurrent airway obstruction (RAO) across various clinical stages and contrasts these features with horses that do not have RAO.

Methods

• The study was carried out with two groups of horses, seven with confirmed RAO and seven who were not affected by RAO (non-RAO).
• Each pair of RAO-affected and non-RAO horses underwent evaluations before, during, and post exposure to hay.
• The assessments consisted of clinical scoring, lung function testing, airway endoscopy, and bronchoalveolar lavage fluid (BALF) absolute and differential cell counts.
• Cell-free BALF was separated into a coarse surfactant pellet and supernatant by ultracentrifugation, and the phospholipid and protein concentrations were measured.
• The phospholipid composition of crude surfactant pellets and surface tension were examined using high-performance liquid chromatography and a pulsating bubble surfactometer respectively.
• The collected findings were compared statistically via mixed-effects, repeated-measures ANOVA.

Results

• The total phospholipid concentration in BALF was lower in RAO-affected versus non-RAO horses at all times of sample collection.
• In the RAO-affected group, the total phospholipid concentration was lower during exposure to hay than before or after exposure.
• There were no significant differences in BALF protein concentration, percentages of phospholipid classes, or surface tension between or within groups of horses.

Conclusions

• All clinical stages of RAO-affected horses were found to have low surfactant concentration in BALF.
• The escalation of RAO led to a further decrease in surfactant concentration.
• The reasons for this lower surfactant concentration in RAO-affected horses are yet to be identified.
• Low phospholipid concentration may make RAO-affected horses more susceptible than unaffected horses to changes in the surfactant. This could contribute to the clinical disease status and progression.