Stimulatory effect of cigarette smoke on the metabolism and covalent binding of benzo(a)pyrene in the trachea of the rat

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Abstract
The activity of aryl hydrocarbon hydroxylase (substrate: benzo(a)pyrene) was increased in the tracheas of rats exposed to cigarette smoke for 1 h daily for either 1 or 10 days. However the degree of increase in activity was lower in the trachea than in the lung. After a single exposure, activity in the trachea was at its highest level 12 h following exposure (3.2‐fold compared to the control), but had returned to the control level within 24 h. Also, the amounts of covalently bound metabolites of benzo(a)pyrene were increased (2‐fold) in nucleic acid and protein fractions of the trachea, when the rats were killed 12 h after a single cigarette smoke exposure. No significant changes in the activity of epoxide hydratase (substrate: styrene oxide) could be detected in the trachea. After repeated exposures the activity of UDP‐glucuronosyltransferase (substrate: methylumbelliferone) was increased (1.7‐fold) in the trachea.