Factors affecting induction of lung aryl hydrocarbon hydroxylase in rats exposed to cigarette smoke.

Induction of lung aryl hydrocarbon hydroxylase (AHH) activity has been studied in rats following their exposure to different regimes of cigarette smoke produced from tobacco and the tobacco substitute NSM. The rate of induction of AHH was maximal during the first 3 days of exposure to tobacco smoke. The frequency of exposure to tobacco smoke was apparently more important in influencing induction of AHH than was the duration of the exposure. After cessation of exposure to smoke, AHH activity declined to control levels within about 3 days. Tobacco smoke was a more potent inducer of AHH than was smoke from NSM. Measurement of AHH may provide a useful means of assessing whether animals involved in toxicity studies of smoking materials inhale sufficient total particulate matter to provoke a biological response, such as induction of AHH.