[Analysis of platelet-activating factor and its effect on the lung].

One of the lipid mediators, platelet-activating factor (PAF), is reported to be involved in a variety of biological phenomena including not only harmful reactions such as allergy or inflammation, but also physiological phenomena like nerve cell differentiation, sperm mobilization, ovulation, implantation, parturition etc. We reviewed the methods of detecting PAF in biological fluids and the effects of PAF on fetal lung maturation and pulmonary diseases. Fetal lung has a capacity to produce PAF and this autacoid is involved in glycogen breakdown to furnish both glycerol backbone, such as dihydroxyacetone phosphate and glycerol-3-phosphate, and the fatty acids utilized to synthesize pulmonary surfactant. PAF also enhances secretion of pulmonary surfactant. However, PAF causes eosinophil recruitment to the lung, activation of eosinophil and neutrophil, bronchoconstriction, and lung edema, and increases bronchial hyperreactivity. All are characteristics of the pathophysiology of bronchial asthma. We examined PAF acetylhydrolase activity in plasma from patients with bronchial asthma, and found the activity was significantly lower in severe cases than that in mild or moderate cases. Ketotifen had no effect on this enzymatic activity. Evaluating PAF acetylhydrolase activity may help determine the severity of bronchial asthma. PAF is also involved in chronic lung disorders of newborns, such as bronchopulmonary dysplasia. We treated a 3-month-old child with frequent pulmonary problems who was made a diagnosis of bronchopulmonary dysplasia during neonatal period. After administration of Ketotifen for one and a half months, his clinical symptoms improved dramatically.