The oxidative metabolism of benzo(a)pyrene and the conjugative metabolism of 1-naphthol by explant cultures of normal human colon and colonic tumor tissue, obtained at surgery, have been studied. After 24 hr in culture, the explants were exposed to either [1-14C]-1-naphthol (20 to 100 µm) or [3H]-benzo(a)pyrene (1.5 µm) for a further 1.5 to 24 hr. Both normal-appearing tissue and tumor tissue metabolized benzo(a)pyrene to a wide variety of organic solvent-soluble metabolites, including monohydroxybenzo(a)pyrenes, dihydrodiols, and tetrols. 1-Naphthol was metabolized by cultured human colonic mucosa and tumor tissue to both its glucuronic acid and sulfate ester conjugates. In the normal tissues, with naphthol (20 µm), sulfate ester conjugation predominated. However, with the tumor tissue, sulfate ester conjugation decreased; thus, the percentage of glucuronic acid conjugates, expressed as a percentage of total metabolites formed, was increased significantly compared to normal tissue. The relationship, if any, of these changes to neoplastic transformation is unclear. The technique of explant culture described in this study may be of use for the study of other facets of the pathobiology of solid tumors.

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This work was supported in part by the Cancer Research Campaign of Great Britain and Interagency Agreement Y01-CP-80204.

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