Regenerative response of the rat tracheal epithelium after acute exposure to tobacco smoke: a quantitative study

The regenerative response of the rat tracheobronchial epithelium after acute exposure to tobacco smoke was studied. Cigarettes were smoked automatically, and the smoke was diluted with air before being inhaled by the animals. Twenty-four hours after the animals were subjected to tobacco smoke, and with vinblastine as a metaphase-arrest agent, a wave of cell proliferation occurred. The intensity of the response was related to the type of smoke (it was more severe for cigarette than cigar tobacco) and depended on the concentration of smoke, but the timing of the response after moderate exposure was constant. The wave of proliferation would appear to be a local response to cell loss or damage, though morphologically the observed changes were slight. With repeated daily exposure, some adaptation of the tissue was apparent, in that the wave of rapid cell reproduction did not recur, but this did not imply that there was no progression of effect with respect to other pathologic processes. The responses to tobacco smoke and sulfur dioxide were compared. Cell proliferation provided a useful and rapid test of certain irritant effects of different types of tobacco smoke, but it was essential that animals free of chronic respiratory disease be used.