Aryl Hydrocarbon Hydroxylase in Human Bronchial Epithelium and Blood Monocyte234

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Abstract
The inducibility of aryl hydrocarbon hydroxylase (AHH) in human bronchial epithelium and blood monocyte was studied in 11 immediate autopsy patients without lung cancer. When the bronchus was exposed to 10 μg of benz[a]anthracene (BA)/ml medium in explant culture, the levels of AHH induction in the bronchus were 3- to 29-fold above control levels. The specific enzyme activity ranged from not detectable (i.e., < 0.14) to 2.9 nmol/hour/mg DNA in untreated tissue and from 1.2 to 30 nmol/hour/mg DNA in BA-treated bronchus. The optimum pH for the bronchus AHH was 7.7. Control AHH and BA-induced AHH in bronchus were both inhibited by 100 μM 7,8-benzoflavone in vitro. Induction of AHH in monocytes ranged from 1.5- to 30-fold above that of controls when the cells were exposed to 2 μg of BA/ml medium in culture. The specific enzyme activity ranged from 1.6 to 19 pmol/hour/106 cells in untreated monocytes and from 5.8 to 53 pmol/hour/106 cells in BA-treated monocytes. The extent of AHH induction in monocytes depended on BA concentration (from 0.1 to 10.0 μg) in a dose-related manner. AHH activity increased linearly with the number of monocytes (from 0.5 to 2×106 ) in the assay system. 7,8-Benzoflavone inhibited the BA-induced but not the basal levels of monocyte AHH activity. The data are consistent with a correlation between the inducibility of AHH in human bronchus and blood monocyte from the same individual.