1986 Volume 8 Issue 2 Pages 183-190
We have been attempting to induce malignant tracheal tumor in adult male beagles in order to examine the process of carcinogenesis by 3-methylcholanthrene (3-MC). We employed a submucosal method in order to stimulate bronchial gland cells and basal cells without stimulation of the mucosal epithelium. Silicone rubber pellets containing 3-MC were surgically implanted in the submucosal layer of the cervical trachea. Monthly bronchoscopical observation was performed for a year. Squamous metaplasia of bronchial gland cells and proliferation of basal cells occurred within a year but there was no particular change in control dogs which only received implantation of silicone rubber pellets. These results suggest that the basal cells and bronchial gland cells may be sites of effectiveness of 3-MC. However, the submucosal implantation method is not useful for long-term experiments because it is difficult to prevent ulcer formation and subsequent exposure and exfoliation of the pellet. On the other hand, we also examined the cytological influence of immuno-suppression on the tracheal epithelium by methylprednisolone acetate. Atypical squamous cell metaplasia could be seen in all immuno-suppressed beagles but not in non immuno-suppressed beagles. It seems that corticosteroids are related to atypical squamous cell metaplasia of the tracheal epithelium.
