AEROSOLIZED SURFACTANT INHIBITS ACETYLCHOLINE-INDUCED AIRWAY-OBSTRUCTION IN RATS

Exogenous surfactant treatment inhibits antigen-induced airway obstruc tion in sensitized guinea-pigs. Aerosolized surfactant also improves r espiratory function in asthmatic patients. The aim of the present stud y was to determine whether aerosolized surfactant inhibits nonallergic airway obstruction induced by acetylcholine. Anaesthetized Wistar rat s were treated by aerosol with the beta(2)-adrenoceptor agonist terbut aline, surfactant (Alveofact(R)), a surfactant-terbutaline combination , or vehicle (control). Animals were then challenged by aerosolized ac etylcholine to elicit receptor-mediated airway obstruction. A second g roup of animals was challenged with intravenous acetylcholine. Respira tory function variables were measured by body plethysmography before a nd after treatment, and after the acetylcholine challenge. Baseline lu ng function values before and after treatment were similar in all grou ps. Acetylcholine challenge by aerosol increased lung resistance by 64 % in control animals. Pretreatment with terbutaline and surfactant sig nificantly limited the increase of lung resistance to +36 and +34%, re spectively. Simultaneous aerosolization of surfactant and terbutaline also inhibited airway obstruction but their effects were not additive. By contrast, terbutaline treatment inhibited the effects of intraveno us acetylcholine, but surfactant did not. In conclusion, we suggest th at surfactant aerosol may prevent acetylcholine and other pharmacologi cal agents from reaching the airway smooth muscle from the airway lume n but not via the bloodstream.