EFFECT OF PLATELET-ACTIVATING-FACTOR ON SECRETION OF MUCOUS GLYCOPROTEIN FROM CHINCHILLA MIDDLE-EAR EPITHELIAL-CELLS IN-VITRO

Platelet-activating factor (PAF) is a naturally occurring phospholipid that acts as a pleiotropic mediator and mediates cell-cell reactions under physiological and pathological conditions. Recently, it has been shown that PAF is a strong secretagogue of mucous glycoprotein in the airways, suggesting its role in mucous glycoprotein secretion and the pathogenesis of otitis media with effusion. In the current study, we examined the effect of PAF on mucous glycoprotein secretion in culture d chinchilla middle ear epithelial cells. PAF at 1 muM significantly s timulated mucous glycoprotein secretion from cultured chinchilla middl e ear epithelial cells. This action was concentration-dependent, with secretions reaching near maximum when the cells were incubated with PA F at 100 muM. In a time-dependent study, PAF demonstrated an initial r apid stimulation of mucous glycoprotein secretion, followed by a gradu al increase thereafter. A six-fold increase was seen in the first 2 h compared with controls. Cycloheximide, a protein synthesis inhibitor, demonstrated an inhibitory effect on PAF-stimulated mucous glycoprotei n secretion in this study. These findings suggest that PAF plays an im portant role in the pathogenesis of otitis media with effusion by stim ulating mucous glycoprotein secretion in vitro.