Effects of Cigarette Smoke on the Bronchial Epithelium of Syrian Hamsters: Ultrastructural Studies 1

SUMMARY-The effects of two types of research cigarettes, which differed in their total smoke delivery and condensate, on the bronchial epithelium of Syrian hamsters were examined electronmicroscopica"y. The animals were exposed once a day for 5 days each week for 1 year to the total smoke of the cigarettes. Two groups and a control group were killed 1 day after the last exposure, and one group 12 months after the last exposure. The bronchial epithelia of a " smoke-exposed animals were hyperplastic, and their ultrastructure showed invaginations, tilt of nuclear axes, an increase in the number and size of Iysosomes and multivesiculated bodies, and in-creased numbers of enlarged intramitochondrial granules. Squamous metaplasia, rarely found, was present at the stage of filamentous bundle formation. The induced alterations were independent of the type of cigarette used. One year after smoking was terminated, the alterations had neither reversed nor advanced, as compared to those occurring 1 day after the last smoke exposure.-J Natl Cancer Inst 55: 353-369, 1975. Over the last 20 years, epidemiologic studies have in-dicated that smoking is important in the etiology of human lung cancer (1); however, knowledge of early smoke-induced alterations in the bronchial epithelium and their subsequent development is minimal. The pres-ent study was, therefore, done to detail the fine structural changes in the bronchial epithelia of Syrian hamsters after chronic smoke exposure, and to determine whether these changes reverse or advance after the experiment is termina ted