FP01-6. HISTOLOTIC CHANGES IN THE EUSTACHIAN TUBE MUCOSA OF RAT AFTER SHORT TERM EXPOSURE OF CIGARETTE SMOKE

Il-Woo Lee, Eui-Kyung Goh, Hwan-Jung Roh, Kyong-Myong Chon (Pusan National University, Korea)

Objective and Background: It is well known that passive smoke is one of the major risk factors for middle ear diseases. But there are no articles addressing the direct relationship between exposure to passive smoke and middle ear disease. Also, there are many conflicting opinions concerning the role of passive smoke in the pathogenesis of middle ear disease. Since eustachiantube mucosa is critical in the development of middle ear disease, this study evaluated the effects that cigarette smoke has on the mucosa of the eustachian tube.

Materials and Methods: Thirty healthy 150- to 230-g Sprague Dawley rats with normal middle ears were used. The animals were devided into six groups of five animals each. Five experimental groups(n=5 each) were exposed to domestic cigarette(This^Ⓡ, tar 7.0mg, nicotine 0.75mg) every 30minutes(total 2.5hours, 5 cigarette total) per day in an in-house constructed smoking chamber for 1, 2, 4, 6, and 8 weeks. A control group (n=5) was placed in the same chamber without exposure to cigarette smoke. After exposure, the animals were sacrificed and cross sections of Eustachian tubes were prepared. Histologic changes of the eusthachian tube mucosa were observed through light and electron microscopes.

Results: Cilia loss, goblet cell depletion, and squamous metaplasia of eustachian tube mucosa were observed after exposure to smoke. Goblet cell counts were decreased by the greatest amount in the one- and two- week exposure groups. The eight-week exposure group had recovered from the decrease. Squamous metaplasia was observed in all experimental groups and at the highest percentage in the eight-week exposure group.

Conclusions: These findings suggest that passive cigarette smoke directly affect eustachian tube mucosa in the early stages of exposure but is reversed in the late stages. A mechanism different from occurring in the respiratory organs such as the nasal cavity and trachea may be activated in the eustachian tube after exposure to passive smoke. The protective function of the eustachian tube may playsome role in this mechanism.

* Contact person email: entgate@pusan.ac.kr