Direct enhancement by cigarette smoke of asbestos fiber penetration and asbestos-induced epithelial proliferation in rat tracheal explants.

Tracheal explants from Sprague-Dawley rats were briefly exposed to cigarette smoke or air (control) and then to amosite asbestos. Asbestos fibers in or under the tracheal epithelium were counted and extent of hyperplastic lesions was ascertained at 24 hours, 72 hours, and 1 week after exposure. Smoke-exposed cultures showed significantly greater numbers of fibers in the epithelium and greater proliferative activity compared to findings in cultures not exposed to smoke. These observations indicate that very short exposure to cigarette smoke can directly affect the response of the epithelium to asbestos fibers and that smoke exposure need not be concurrent with asbestos exposure for such event to occur. These reactions may play a role in the greater incidences of lung cancer and asbestosis seen in asbestos-exposed workers who smoke.