Background: Lung surfactant function and composition are varied and adapted to the specific respiratory physiology of all mammalian species.
Hypothesis: Lung surfactant function and composition are different in neonatal foals as compared to adult horses.
Animals: Six adult horses, 7 term foals (<24 hours old), and 4 premature foals were used. Animals were part of the Auburn University teaching herd except for 3 client-owned premature foals.
Methods: Bronchoalveolar lavage fluid (BALF) was obtained from all animals. Ultracentrifugation of cell-free BALF separated surfactant into crude surfactant pellets (CSP) and supernatant. Both fractions were analyzed for phospholipid and protein content with the Bartlett and bicinchoninic acid method, respectively. Phospholipid composition of the CSP was determined by using high-performance liquid chromatography with an evaporative light scatter detector. Surface tension of the CSP was measured with a pulsating bubble surfactometer. Results from term foals (<24 hours old) were compared statistically to those from adult horses. Values of P < .05 were considered significant.
Results: BALF phospholipid content was similar between adult horses and term foals, but BALF protein content was significantly decreased in term foals. Phosphatidylglycerol was significantly decreased, phosphatidylinositol was significantly increased, and the minimum surface tension was significantly increased in the CSP from term foals compared to adult horses.
Conclusions and clinical importance: Surface tension and phospholipid composition of surfactant in neonatal foals are significantly different compared to adult horses. These changes may influence biophysical and immunologic functions of surfactant.