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Metabolism of benzo(a)pyrene by tracheal epithelial cells.

Santos, Meiri dos. (1978) Metabolism of benzo(a)pyrene by tracheal epithelial cells. Doctoral thesis, University of Surrey (United Kingdom)..

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One of the major aims of this study was to develop a method for the isolation and maintenance of tracheal epithelial cells in both suspension and culture, such epithelial cells could then be used as a valid experimental system for respiratory carcinogenesis studies. In this study, I describe for the first time the isolation of viable tracheal epithelial cells. The method described gives a good yield of viable cells, most of which appear to be ciliated. The cells were characterised by various biochemical and histochemical assays. One major advantage of such isolated cells is the preservation of both Phase I and Phase II metabolising enzymes under conditions similar to those found in vivo. These isolated cells were then used as starting material for the cell culture, and a cell monolayer was obtained. The cells were grown in the presence of serum and were highly proliferative. Human carcinoma arises in epithelium and is the predominant form of human cancer, therefore it is important to study the tissue of origin for the amounts of carcinogens metabolized and the types of products formed. Aryl hydrocarbon hydroxylase activity was present in significant amounts in the freshly isolated tracheal cells. Treatment of the cultured cells with 3-methylcholanthrene, benz(a)anthracene and benzo(a)pyrene increased the activity of the enzyme, and the best inducer was benz(a)anthracene. The metabolism of benzo(a)pyrene was studied in lung and trachea short-term organ culture, in freshly isolated cells and cultured cells. A chromatographic investigation of the metabolic products has show that the major ethyl acetate-soluble metabolite formed by freshly isolated cells was 3-hydroxybenzo(a)pyrene, while with short-term organ culture and in the cultured cells, the major metabolite formed was 9,10-dihydro-9,10-dihydroxybenzo(a)-pyrene. This difference was probably due to the time of incubation (6 hours only). Other metabolic products identified were 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene, 4,5-dihydro-4,5-dihydroxybenzo(a)pyrene and 3-hydroxybenzo(a)pyrene. In cell culture, a water-soluble glucuronide conjugate of 3-hydroxybenzo(a)pyrene was identified. The presence of further metabolites such as catechols and quinones was also observed. The production of 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene by the cultured epithelial cells was significant, since this compound is further metabolized to an active alkylating agent, 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene-9,10 oxide, which binds to DNA and may be the ultimate carcinogen of benzo(a)pyrene. Thus, tracheal epithelial cells, which are susceptible to hydrocarbon carcinogenesis are capable of metabolically activating benzo(a)pyrene to its suspected proximate carcinogen and probably to the ultimate carcinogen. Thus the systems developed in these studies would appear to be suitable model systems for the study of respiratory carcinogenesis. Such systems may also be used for the study of environmental and other toxic agents which act on cells of the upper respiratory tract.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Santos, Meiri dos.
Date : 1978
Contributors :
Additional Information : Thesis (M.Phil.)--University of Surrey (United Kingdom), 1978.
Depositing User : EPrints Services
Date Deposited : 22 Jun 2018 14:26
Last Modified : 06 Nov 2018 16:53

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