Inhalation of endotoxin stimulates alveolar macrophage production of platelet-activating factor.

The production of PAF was studied in alveolar macrophages (AM) and neutrophils recovered by bronchial lavage from guinea pigs exposed to aerosolized bacterial endotoxin (lipopolysaccharide, LPS). The amount of cell-associated PAF was estimated by measuring serotonin release from rabbit platelets. An increased and dose-related production was found in AM for as long as 2 h after a 40-min exposure. No production was detectable after 4 h. Prolonging the exposure did not prolong the response. When a second exposure was given, no PAF could be detected until the time interval between the 2 exposures was 72 h. The amount of neutrophils in lung lavage fluid was elevated about 100 times at 4 h after the exposure, but only a minor PAF production was found in these cells. In view of the role of LPS-contaminated dusts for the development of human lung disease, particularly airway constriction, the role of PAF needs to be further investigated.