Effect of NO2 and SO2 inhalation on benzo(a)pyrene metabolism in rat lung.

Male Wistar rats were continuously exposed to NO2 (14.4 ppm), SO2 (46.5 ppm) and to a mixture of both gases and their effect on lung microsomal aryl hydrocarbon (benzo(a)pyrene) hydroxylase (AHH) activity was determined. The pre-exposed animals were administered methylcholanthrene (MC) to investigate the exposure effect on enzyme inducibility and pattern of B(a)P metabolites. NO2 significantly increased AHH activity but no marked change was noted with SO2. Induction of AHH by MC was markedly inhibited by SO2, only slightly by mixture of NO2-SO2 but not with NO2 alone.