[Increased plasma levels of platelet-activating factor (PAF) and low serum PAF acetylhydrolase (PAFAH) activity in adult patients with bronchial asthma].

We studied the relationship between the blood levels of platelet-activating factor (PAF) and the activity of serum PAF acetylhydrolase (PAFAH), an enzyme that inactivates PAF, in adult patients with bronchial asthma. The PAF levels in the blood and the PAFAH activity in the serum obtained from adult patients with bronchial asthma in remission (137 cases) and from healthy adult controls (106 cases) were determined by radioimmunoassay (RIA) and compared. The following results were obtained. 1. The plasma levels of PAF were significantly higher in the patients with bronchial asthma in all severity groups (mild, moderate, and severe) and all asthma types (atopic, mixed, and infectious) than in the healthy controls (p < 0.001). However, no significant differences associated with the severity and type of asthma were noted. 2. Serum PAFAH activity was significantly lower in the patients with bronchial asthma in all severity groups (mild, moderate, and severe) and asthma types (atopic, mixed, and infectious) than in the healthy controls (p < 0.001). However, no significant differences associated with the severity and type of asthma were noted. 3. PAF/PAFAH in the patients with bronchial asthma showed no significant difference associated with the severity and type of asthma. 4. There was not a significant correlation between plasma levels of PAF and serum PAFAH activity in the patients with bronchial asthma. It was, therefore, suggested that the significantly high plasma PAF levels and the significantly low serum PAFAH activity in asthmatic adults compared to the respective values in healthy controls may explain one of the mechanisms of the development and persistency of adult bronchial asthma.