Activities of drug metabolizing enzymes in bovine colon epithelial cell cultures.
The metabolic competence of cultured bovine colon epithelial cells was evaluated by determining activities of phase I and II enzymes in colonocytes cultured for different intervals (maximum of 10 days) compared with activities measured in freshly isolated cells. Cytochrome p50 1A1-associated 7-ethoxyresorufin O-deethylase (EROD) activity was detectable in freshly isolated colonocytes and in colon cells maintained in culture for up to 5 days. In contrast to liver samples, cytochrome p50 3A4-associated 7-benzyloxyresorufin O-debenzylase (BROD) activity was not detectable in bovine colon cells. Prostaglandin H synthase-mediated production of prostaglandin E(2) was found in freshly isolated and also in cultured colonocytes. Both isoenzymes (COX 1 and COX 2) were detected in cultured cells. To examine phase II metabolic potency, activities of N-acetyltransferases 1 and 2, of phenol and amino sulfotransferases, of glutathione S-transferases alpha, mu, pi and theta and of UDP-glucuronyltransferase were measured. N-Acetyltransferase (NAT) activity (substrate p-aminobenzoic acid, PABA, a diagnostic substrate for the human NAT-1 enzyme) was stable under culture conditions and during the observed culture period comparable to that of freshly isolated cells. In contrast, sulfamethazine, a specific substrate for NAT-2, was not acetylated, neither in bovine colon cells nor in bovine liver samples. Whereas activity of amino sulfotransferase (substrate 2-naphthylamine) decreased continuously during the entire culture period, the activity of phenol sulfotransferase (substrate 1-naphthol) decreased only slowly. Activity of total glutathione S-transferases (alpha, mu, and pi) (substrate 1-chloro-2,4-dinitrobenzene) decreased after 2 days in culture, but was stable during the following culture period. Activity of glutathione S-transferase theta (substrate epoxy-3-nitrophenoxypropane) changed during the culture period. At the beginning and the end (after 10 days) of the culture period maximum activity was measured. Activity of UDP-glucuronyltransferase increased during the culture period reaching a maximum after 7 days. The results show that cultured bovine epithelial colon cells express several enzyme activities required for the biotransformation of xenobiotics.
D000818:Animals; D015415:Biomarkers; D002417:Cattle; D002478:Cells, Cultured; D003106:Colon / Q000201:enzymology*; D003470:Culture Media; D003600:Cytosol / Q000201:enzymology; D004847:Epithelial Cells / Q000201:enzymology*; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D008862:Microsomes, Liver / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000096:biosynthesis; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015262:Xenobiotics / Q000378:metabolism
D015415:Biomarkers; D003470:Culture Media; D004364:Pharmaceutical Preparations; D012333:RNA, Messenger; D015262:Xenobiotics; D006899:Mixed Function Oxygenases