Exudative, cellular and humoral reactions to platelet-activating factor (PAF-acether) in the pleural cavity of rats

Abstract The reactions to platelet-activating factor (PAF-acether) injected into the pleural cavity of rats were compared with the reactions in animals injected with 0.9% NaCl. PAF-acether induced a maximum exudate after 30–60 min, which then decreased and disappeared after 24 h. The number of pleural leukocytes in the exudate was clearly decreased 30 min after the injection, was slightly increased after 6 h and was unchanged at other times. The estimation of lipid mediators in the pleural exudate obtained 30 and 60 min after the injection of PAF-acether revealed an increase in type-C 4 leukotriene (LTC 4 ) and a decrease in thromboxane B 2 (TxB 2 ) and in 6-keto prostaglandin F 1α (6-keto PGF 1α ). In addition, the amount of histamine was found to be lower after 30 min. These results confirm in vivo that some biological effects of PAF-acether seem to involve the participation of other mediators.