The anaphylactic release of platelet‐activating factor from perfused guinea‐pig lungs

1 The release of platelet‐activating factor (Paf‐acether) and of its inactive precursor/metabolite lysoplatelet activating factor (lyso‐Paf) from control and sensitized guinea‐pig isolated lungs challenged with antigen was investigated. 2 Control guinea‐pig lungs perfused either through the pulmonary circulation or through the airways and challenged with antigen did not release Paf‐acether. 3 Sensitized guinea‐pig isolated lungs perfused through the pulmonary circulation and challenged with antigen released lyso‐Paf but not Paf‐acether. 4 Sensitized guinea‐pig isolated lungs perfused through the airways and challenged with antigen released three times more lyso‐Paf and also Paf‐acether. 5 These results support a possible role for Paf‐acether in respiratory anaphylaxis in the guinea‐pig.