Platelet-activating factor in bronchoalveolar lavage fluid of patients with adult respiratory distress syndrome.

1. To clarify the role of platelet-activating factor (PAF) in the development of adult respiratory distress syndrome (ARDS), we performed bronchoalveolar lavage (BAL) in 19 patients with ARDS and examined cell populations, albumin concentrations and PAF levels. PAF levels were measured by a newly developed radioimmunoassay. 2. In the BAL fluid of ARDS patients, neutrophil percentages and albumin concentrations markedly increased compared with control subjects. 3. PAF was detected in 14 of 19 patients with ARDS, whereas it did not exist in the control subjects. 4. Furthermore, we investigated the priming effect of recombinant human tumour necrosis factor-alpha (TNF alpha), which is known to be one of the most important mediators in the development of ARDS, on PAF production induced by the calcium ionophore in neutrophils. 5. Pre-incubation with TNF alpha dose-dependently increased both extracellular and intracellular PAF production in neutrophils. 6. These results suggest that PAF might play an important role in the development of ARDS.