Effects of platelet activating factor on mucociliary clearance of the eustachian tube

The effects of platelet activating factor (PAF) on mucociliary clearance of the eustachian tube were investigated both in vitro and in vivo. Normal ciliated epithelium was obtained from the eustachian tube of guinea pigs and incubated with PAF at concentrations ranging from 10(-10) to 10(-6) mol/L. Ciliary activity was observed under an inverted microscope and quantified photoelectrically. The PAF dose-dependently inhibited ciliary activity. One milliliter each of 10(-5) mol/LPAF, 10(-5) mol/L prostaglandin E2 (PGE2), 10(-5) mol/LPAF and PGE2, or the control solution (0.1 v/v% methanol-phosphate-buffered saline) was directly injected into the tympanic bullae of anesthetized chinchillas. The middle ear was examined by otomicroscopy, tympanometry, and auditory brain stem response in relation to time. The PAF delayed middle ear clearance, and the PGE2 augmented its delay. These findings suggest that PAF inhibits mucociliary clearance of the eustachian tube from the middle ear, and that PGE2 plays an important role in the augmentation of inflammatory disorders.