Effects of cigarette smoke dose and time after smoke exposure on uptake of asbestos fibers by rat tracheal epithelial cells

We have previously shown that exposure of excised rat tracheal segments to cigarette smoke followed by exposure to a solution of amosite asbestos increases uptake of asbestos fibers compared to exposure to air followed by asbestos. To learn more about the mechanism of smoke-enhanced fiber uptake, we evaluated the effects of amount of smoke and time delay between smoke exposure and asbestos exposure on fiber penetration into the epithelium. To determine whether amount of smoke exposure affected this process, we exposed tracheal segments to 1, 3, or 6 puffs of smoke and subsequently to 5 mg/ml amosite asbestos for 1 h. The segments were then maintained in organ culture for up to 7 d. Asbestos uptake was evaluated by counting fibers in the epithelium by light microscopy. Exposure to increasing numbers of puffs of smoke produced a dose-related increase in fiber uptake at 1 d, 3 d, and 7 d after exposure. To determine whether asbestos exposure needed to occur immediately after smoke exposure for enhanced uptake of fibers to occur, we exposed tracheal segments to 6 puffs of smoke and then delayed exposure to asbestos for 0 (immediate exposure), 3, 18, or 48 h. Tracheas were again maintained in organ culture for up to 7 d after asbestos exposure. Delayed exposure to asbestos after 6 puffs of smoke produced an increase in fiber uptake, even with an interval as long as 48 h between smoke and asbestos exposure; however, the absolute magnitude of fiber uptake was less than that seen with immediate postsmoke asbestos exposure. If catalase was added to the asbestos solution, the smoke-enhanced uptake was abolished, no matter what the time delay.(ABSTRACT TRUNCATED AT 250 WORDS)