Morphology, Physiology and Pathology of Eustachian Tube. Pathophysiology of the Mucociliary System in the Eustachian Tube.

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Other Title
  • 耳管の形態・機能および病態　耳管の粘液線毛機能の生理と病態
  • Pathophysiology of the Mucociliary System in the Eustachian Tube
  • 耳管の粘液線毛機能の生理と病態

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Abstract

The eustachian tube is embryologically formed by an invagination of the nasopharyngeal mucosa, and is an extension and modification of the respiratory mucosa, which is composed of ciliated cells and mucus blanket. Therefore, the eustachian tube has a functional mucociliary system, which plays a key important role in the defense mechanism of the tubotympanum. Our study has concerned the pathophysiology of the mucociliary system induced by a variety of pathological factors including endotoxin, allergic inflammatory mediators, and allergic responses. This study has also experimentally discussed the possible preservative medication for otitis media with effusion.<BR>Ciliary activity of the eustachian tube decreased in a doser esponse fashion in the presence of bacterial endotoxin. Intratympanic inoculation of bacterial endotoxin induced ciliary depression and prolonged mucociliary clearance of the eustachian tube, resulting in middle ear effusions. Intratympanic inoculation of a larger concentration of endotoxin resulted in a longer persistence of middle ear effusions.<BR>We examined the effect of histamine and its H1 and H2 blockers on the eustachian ciliary activity. Ciliostimulatory effects were demonstrated for histamine. Such ciliostimulatory effects were not affected by Hl-blocker but were reduced by H2-blocker. Therefore, histamine could enhance ciliary activity through combining with H2-receptor. Intratympanic injection of histamine induced accumulation of middle ear effusions and mucociliary dysfunction. The duration of the pathology depended on the concentration of histamine for intratympanic injection.<BR>Platelet activating factor (PAF) had no effect on the in vitro ciliary activity, but reduced ciliary activity in the presence of bronchoalveolar lavage fluid in a dose response fashion. Intratympanic injection of PAF induced mucociliary dysfunction and eosinophil accumulation in the eustachian tube, resulting in middle ear effusions.<BR>Roxythromycin (RXM) and a Chinese medicine, Sai-rei-to are reported to have a ciliostimulatory effect. We examined whether pretreatment with these drugs could prevent the middle ear from endotoxin-induced otitis media with effusion. Guinea pigs were treated with two doses of these drugs for two weeks. Then bacterial endotoxin was inoculated into their tympanic cavities. Sai-reto alleviated the endotoxin-induced mucociliary dysfunction and accumulation of middle ear effusions in a dose response fashion. RXM also alleviated such endotoxin-induced pathologies, but such effects were not dependent upon the concentrations of RXM administered.<BR>An inference has been derived from the study that the mucociliary system of the eustachian tube plays a key important role and easily damaged by a variety of irritant factors and that ciliostimulatory medication could be useful in the treatment of recurrent otitis media with effusion.

Journal

  • Otology Japan

    Otology Japan 5 (3), 179-188, 1995

    Japan Otological Society

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