기관지상피화생에 관한 실험적 연구

Abstract

Bronchial epithelial metaplasia of the rabbits was experimentally studied by means of long-standing repeated inhalation of formalin gas, Used animals were healthy adult rabbits weighing about 1,5 kgm, and having _ no pulmonary diseases. Formalin gas was administered according to Hollands" method and eleven sections were taken from the definite sites of the trachea and both main bronchi. The following results and conclusions were made. 1. In the group which was not exposed to the formalin gas inhalation typical squamous metaplasia of bronchial epithelium in the course of time was not observed. 2. In the group which was exposed to the repeated formalin gas inhalation inflammatory changes, degenerative changes, regenerative findings especially metaplastic change and complicated reparative changes were observed: ® In the group which was exposed to the repeated formalin gas inhalation, a certain serial changes; i.e., destruction and desquamation of columnar epithelium, newgrowth of single layered squamous epithelium and proliferation of multilayered squamous epithelium (metaplasia) were observed in early stage(l-18 experimental days). (Q) In the group which was exposed to the repeated formalin gas inhalation various changes ranging from degeneration, destruction or desquamation of squamous epithelium to regenerated columnar epithelium, and also ranging from relatively normalcolumnar epithelium to typical stratified squamous metaplasia were observed in early phase of middle stage(l9-43 experimental days). © In the group which was exposed to the repeated formalin gas inhalation various gradational changes described above were observed in the trachea and bronchi, and moreover, papillary projections of bronchial metaplastic epithelium were observed in a considerable proportion, and also characteristic alveolar epithelialation was observed in one case, in late phase of middle stage(44-64 experimental days). @ In the group which was exposed to the repeated formalin gas inhalation the earliest case showed rather typical squamous metaplasia of trachea and bronchi after five hours of actual exposure. 3. In the group which was exposed to the long-continued and repeated formalin gas inhalation(65-283 experimental days) a certain serial changes described above were observed, and in this group more marked keratinizing stratified squamous metaplasia and conspicuous papillary projection of metaplastic epithelium were observed. In most cases, moderate to marked bronchiectatic changes were observed in lower parts of the lungs. 4. In the group which was exposed to the repeated formalin gas inhalation findings consistent with atypical metaplasia or carcinoma in situ were not observed. 5. In the group which was exposed to the repeated formalin gas inhalation the incidence of epithelial metaplasia of trachea and bronchi was approximately 80 per cent. Male rabbit (92% positive) showed definite high positivity compared to the female rabbit (approximately 69% positivity). 6. In the group which was exposed for long time(96% positive) metaplastic tendency was apparantly increased compared to that of short-term exposure group (62% positive). 7. Observations on distribution and range of metaplasia failed to indicate the site preponderance in trachea and bronchi. 8. In the group which was exposed to the repeated formalingas inhalation invasiveness of metaplasia was relative ly high and it was especially conspicuous in the group of long-continued exposure.