Background The cause of the airway resistance developing during an asthma attack is not completely understood. Besides bronchospastn and airway oedema a surfactant dysfunction has been suggested as a reason for an increased airway resistance.
Objective This paper airns at exatnining if itideed surfactant dysfunction develops when an asthma attack is induced in guinea-pigs.
Methods Guinea-pigs, immunized against ovalbumin and ihcn challenged (by inhal-ing the antigen) underwent lung function tests (n=7) and were compared with seven animals challenged, but not immunized. Lung lavage was carried out in three groups of guinea-pigs: controls. never immunized nor challenged (n=7), not immunized but challenged (n=6), immunized and challenged, no lung function test (n=6). After concctUruting the tavage fluit 10 times the surface activity was evaluated wilh the pulsatitig bubble surfactometer. The fluid's concentration of phospholipids and proteins was determined as was ihe phospholipid composition.
Results The 19 immunized and challenged animals all developed severe respiratory distress, six so seriously that they died. Lung function tests showed significantly increased airway resistance and decreased tidal volume, minute volume, and dynamic compliance. Surface activity of lavage fluid from immunized and challenged animals was significantly reduced when compared with fluid from control animals (p<0.01). Immunization and challenge had no effect on the lavage fluid's phospholipid concen-tration or composition, but the proteins were at a higher concentration that in ihe fluid of the controls (P<0.01).
Conclusion Proteins leaking into the airways inhibited the surfactant. This, in turn might have caused conducting airways to become blocked by liquid columns, which would increase airway resistance.
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