Abstract
Bronchial asthma is characterized by increased airway responsiveness and reversible bronchial constriction. The bronchial hyperreactivity is associated with localized inflammation and related to chemical mediators in the airway. Platelet-activating factor (PAF) is one of these mediators. Previous reports showed that inhaled PAF caused a bronchoconstriction in man. They suggested that PAF may contribute to the pathogenesis of bronchial hyperresponsiveness, which is the most characteristic abnormality in asthma. In the present study, PAF was detected in sputa from asthmatics and patients of various pulmonary diseases. The amounts of PAF in sputa which were quantified by bioassay using washed rabbit platelets aggregation were, respectively,0.73 ± 0.32,1.27 ± 0.98,17.82 ± 11.42 and 0.15 ± 0.08 pmol/ml (mean ± standard error) for the patients with bronchial asthma (n = 22), pulmonary emphysema (n = 5), chronic bronchitis (n = 4) and pneumonia (n = 4). Additionally, some of the patients were tested for bronchial responsiveness by a methacholine bronchial provocation test by an Astograph at the same time of sputum collection (n = 19). The data of bronchial responsiveness were not correlated with the amounts of PAF. A close correlation was found between PAF amounts and leukocytes counts in sputa from asthmatics (p< 0.01, r=0.90, n=22), especially neutrophils counts (p< 0.01, r=0.91, n=18). Adding other diseases, there was also a significant correlation between PAF amounts and leukocytes counts (p< 0.01, r =0.89, n=35) or neutrophils counts (p< 0.01, r =0.88, n=28). However, no relationship between the amounts of PAF and the number of eosinophils or lymphocytes was shown. These findings do not support a conclusion that PAF is a specific chemical mediator in asthmatic response. PAF is considered to be commonly present in the airway inflammatory lesion related to neutrophils.
