SURFACTANT DYSFUNCTION DEVELOPS WHEN THE IMMUNIZED GUINEA-PIG IS CHALLENGED WITH OVALBUMIN AEROSOL

Background The cause of the airway resistance developing during an asthma attack is not completely understood. Besides bronchospasm and airway oedema a surfactant dysfunction has been suggested as a reason for an increased airway resistance. Objective This paper aims at examining if indeed surfactant dysfunction develops when an asthma attack is induced in guinea-pigs. Methods Guinea-pigs, immunized against ovalbumin and then challenged (by inhaling 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 concentrating the lavage fluid 10 times the surface activity was evaluated with the pulsating bubble surfactometer. The fluid's concentration of phospholipids and proteins was determined as was the 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 concentration or composition, but the proteins were at a higher concentration than in the 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.