Desensitization to PAF-induced bronchoconstriction and to activation of alveolar macrophages by repeated inhalations of PAF in the guinea pig.

Guinea-pig alveolar macrophages are activated in the presence of PAF-acether (PAF), as shown by O2.- production, suggesting that these cells, abundant in the lungs, are involved in PAF-induced bronchoconstriction. Alveolar macrophages collected after in vivo desensitization to the bronchoconstrictor effect of PAF became refractory to it in vitro, whereas the O2.- production in response to f-met-leu-phe persisted, although it was diminished suggesting a partial cross-desensitization. A similar desensitization to PAF was also observed in alveolar macrophages in vitro, demonstrating a stimulus-specific process. This study suggests that alveolar macrophages may be involved in bronchoconstriction induced by aerosol of PAF.