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Keywords:

  • airway inflammation;
  • airway patency;
  • asthma;
  • surfactant dysfunction;
  • alveolar type II cells;
  • surfactant synthesis

Summary

Background Asthma symptoms may partially be caused by a surfactant dysfunction. The inflammatory reaction, so characteristic of asthma, involves a protein invasion of airways which harmfully affects the surfactant function. However, mild asthma attacks might also impede the surfactant synthesis in alveolar type II cells.

Objective The present study evaluates the hypothesis that type 11 pneumocyte metabolic function might be disturbed in a model of mild asthma.

Methods Immunized, as well as not immunized control guinea-pigs, were challenged three times at two-day intervals with 0.04% ovalbumin aerosol. Bronchoalveolar lavage (BAL) was performed one day after the last challenge and the fluid was evaluated for surface activity, and content of phospholipids and proteins. Alveolar type II cells were isolated and their ability to incorporate a 3H labeled surfactant precursor was evaluated.

Results BAL fluid from immunized and challenged animals showed less surface activity (P < 0.01) when compared with BAL fluid from controls, not immunized but challenged. Most likely the reduced surface activity was caused by a 14% increase in the protein concentration (P < 0.05). Isolated type II cells from immunized and challenged animals had 33% less phospholipids than cells from controls (P < 0.05), and phosphatidylcholine synthesis was reduced 35% (P < 0.05).

Conclusion Conclusion These results suggest that the synthesis, intra-cellular storage, and biophysical activity of surfactant are decreased in an intermittent and mild form of asthma.