Influence of age on surfactant isolated from healthy horses maintained on pasture.
Authors: Christmann U, Hite R D, Witonsky S G, Elvinger F, Werre S R, Thatcher C D, Tan R H H, Buechner-Maxwell V A
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Age-Related Changes in Equine Pulmonary Surfactant Pulmonary surfactant dysfunction has been documented in horses following various stressors—exercise, anaesthesia, transport—and in disease states such as recurrent airway obstruction, yet little was known about how ageing affects surfactant composition in healthy animals or how sampling technique influences results. Christmann and colleagues collected bronchoalveolar lavage fluid (BALF) from 15 healthy pasture-kept horses aged 6–25 years, then separated and analysed the crude surfactant pellet and supernatant fractions using ultracentrifugation, high-performance liquid chromatography, and pulsating bubble surfactometry to assess phospholipid content, composition, and surface tension-lowering function. Advancing age was associated with a significant decrease in phospholipid content within the crude surfactant pellet, though protein levels and the functional properties of surfactant remained unchanged regardless of horse age. These findings suggest that age-related changes to lung parenchyma may gradually deplete surfactant phospholipids without impairing surface-active properties, and they validate BALF collection protocols with recovery rates of at least 50% as reliable for surfactant assessment across age groups. For practitioners managing older horses with respiratory concerns, this work provides a baseline understanding of normal age-related surfactant changes, helping distinguish physiological senescence from true surfactant dysfunction secondary to disease or acute insult.
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Practical Takeaways
- •Older horses show age-related decreases in surfactant phospholipid content despite maintained functional capacity, which may reflect normal aging of the pulmonary system
- •When collecting bronchoalveolar lavage samples for surfactant analysis, aim for at least 50% fluid recovery to ensure reliable interpretation of results independent of age
- •Age-related surfactant changes in healthy horses are not clinically concerning as composition and function remain unaffected
Key Findings
- •Increasing age was associated with decreased phospholipid content in crude surfactant pellet (CSP) but not in surfactant supernatant
- •Age did not affect protein content of CSP or surfactant supernatant, or surfactant phospholipid composition or function
- •Age-related surfactant changes were independent of bronchoalveolar lavage fluid recovery percentage, nucleated cell count, and cytological profile
- •Surfactant composition remained stable regardless of BALF sample characteristics when recovery percentage was at least 50%