The Experimental Study Of Platelet Activating Factor On Middle Ear Epithelial In Guinea Pigs

Background and Objective: Secretory otitis media (SOM) is a kind of common and crinose disease on the clinic, especially in children, and it is one of the most common causes of the hearing loss in children. The etiology and pathogenesis of SOM is very complex, and although many internal and external scholars have researched on it for many years, it is not very clear now. Recently, the viewpoint that the inflammation and the inflammatory mediators produced by the inflammatory induction take part in the pathogenesis of SOM have attracted the people attentions gradually, and many investigators found that a lot of inflammatory mediators with biological activities might have important roles in the production of SOM. Platelet activating factor (PAF) is the most powerful inflammatory mediators, and so, in the present research, we detected and quantified the PAF in the middle ear effusions of the SOM patients, and researched the effects of PAF on the mucociliary clearance system~ secretory reaction and vascular permeability of the middle ear mucosa both in vitro and in vivo, in order to elucidate the possible mechanism of the SOM induced by PAF, and furthermore, to show the roles of the inflammatory mediators in the etiology and pathogenesis of SOM. Methods: 1. The PAF in the middle ear effusions of the SOM were detected and quantified by the reverse-phase high performance liquid chromatography system (RP-HPLC). 2. The experiments in vivo: PAF of different concentrations were injected into the right middle ear bullae of the guinea pigs, the left compared as the control, then the bilateral tympanic membranes were observed by the operation microscope; and the dye transport time (DTF, the time from the tympanunl to the nasopharyngeal orifices of the eustachian tube ) was measured; in addition, the vascular permeability (VP) of the middle ear mucosa was measured by the Evans blue vital dye technique. 3.The experiments in vitro: PAP was added into the cultured middle ear epithelial cells of the guinea pigs, and the mucous glycoprotein (MOP) in the supernatant were measured by the radioactivity to describe the effects of PAF on the MGP secretion. Results: 1. PAP is really existent in the middle ear effusions of SOM patients, and the percentage of the samptes in which the PAP could be deteehed is 57.7%. Additionally, the PAP level in the mucoid middle ear effiisions was 78.17 5.77ng/ml, which was higher than that in the serous middle ear effusions (42.38 7.53ng/ml). 2. The experiments in vivo: we found that after the injection of PAP into the middle ear bullae of the guinea pigs the middle ear effusions were produced, and the ABR thresholds increased. The histopathology of the middle ear mucosa showed a degree of middle ear mucosal inflammations were present in all experimental groups, such as edema hyperemia focal hemorrhage inflammatory cells infiltration, et al, some could be found the existence of the mucus plug. The ultrastucture of the middle ear mucosa remained intact approximately Along with the increase of the PAP concentrations and the action time, the DTT was delayed gradually, and the fluctuation of the dye front which could be seen in the nasopharyngeal orifices of the eustachian tube of the control groups disappeared in the experimental groups. By measuring the absorbances of the exudative dye in the middle ear mucosa, we found that compared with the controls, the VP of the middle ear mucosa increased significantly. - 3. The...