Slow-reacting substance from alveolar macrophages--a mechanism of asthma?

The effects of alveolar macrophages on bronchial reactivity were studied in vitro to determine whether these cells could provide a pathogenetic link between cellular components of the inflammatory response, chemical medication of smooth muscle contraction and possible local mechanism of asthma. Alveolar macrophages harvested from rabbit lungs produced consistent and prolonged contractile responses in guinea-pig tracheal rings. The contractile material had the pharmacological and physical properties of slow-reacting substance (SRS) and, in particular, it was completely antagonized by minute concentrations (5 ng/ml) of a specific SRS antagonist, FPL 55712. The average contractile response per 10(6) macrophages was quantitatively equivalent to that produced by 76 ng methacholine. These findings not only support the view that local mechanisms may be of relevance in the pathogenesis of asthma, but could also have possible implications for therapy.