Carcinogen Metabolism Studies in Human Bronchial and Lung Parenchymal Tissues

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Abstract
The pulmonary metabolism of xenobiotics was investigated by measuring the glutathione content and the activity of the aryl hydrocarbon hydroxylase, epoxide hydrolase, glutathione S- transferase, and uridine 5′-diphosphoglucuronosyl transferase enzymes in S-12 fractions of bronchial tree and peripheral lung parenchyma obtained at surgery from 21 patients. In parallel, the same preparations were used to assess either the activation of promutagens, i.e., benzo(a)pyrene, 2-aminofluorene, cyclophosphamide, and a cigarette smoke condensate, to metabolites reverting his Salmonella typhymurium strains, or the decrease of direct-acting mutagens, i.e., sodium dichromate, 4-nitroquinoline N-oxide, epichlorohydrin, and ICR 191. As compared to bronchus preparations, parenchymal preparations contained considerably higher concentrations of reduced glutathione, had a significantly higher epoxide hydrolase activity, and, as assessed by means of a quantitative index, were more efficient in activating 2-aminofluorene and in reducing the mutagenicity of dichromate and 4-nitroquinoline N-oxide. These data may suggest that parenchymal lung tissue is more capable than bronchial tissue to detoxify reactive intermediates of xenobiotics, possibly explaining the greater susceptibility of bronchi to cigarette smoke-induced cancers.

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