Abstract
Predictive in vitro methods to investigate drug metabolism in the human intestine using intact tissue are of high importance. Therefore, we studied the metabolic activity of human small intestinal and colon slices and compared it with the metabolic activity of the same human intestinal segments using the Ussing chamber technique. The metabolic activity was evaluated using substrates to both phase I and phase II reactions: testosterone, 7-hydroxycoumarin (7HC), and a mixture of cytochrome P450 (P450) substrates (midazolam, diclofenac, coumarin, and bufuralol). In slices of human proximal jejunum, the metabolic activity of several P450-mediated and conjugation reactions remained constant up to4hof incubation. In the colon slices, conjugation rates were virtually equal to those in small intestine, whereas P450-mediated conversions occurred much slower. In both organs, morphological evaluation and ATP content implied tissue integrity within this period. P450 conversions using the Ussing chamber technique showed that the metabolic rate (sum of metabolites measured in apical, basolateral, and tissue compartments) was constant up to 3 h. For 7HC conjugations, the metabolic rate remained constant up to 4 h. The distribution of the metabolites in the compartments differed between the substrates. Overall, metabolic rates were surprisingly similar in both techniques and appear similar to or even higher than in liver. In conclusion, this study shows that both human intestinal precision-cut slices and Ussing chamber preparations provide useful tools for in vitro biotransformation studies.
Footnotes
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This study was supported by AstraZeneca, the Technology Foundation STW, Applied Science Division of NOW, and the Technology Programme of the Ministry of Economic Affairs, as well as Yamanouchi Europe.
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.106.011148.
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ABBREVIATIONS: TT, testosterone; 7HC, 7-hydroxycoumarin; P450, cytochrome P450; TFA, trifluoroacetic acid; 7HC-GLUC, 7-hydroxycoumarin glucuronide; TOH, hydroxytestosterone; WME, Williams medium E; 7HC-SULF, 7-hydroxycoumarin sulphate; ACN, acetonitrile; MeOH, methanol; KBR, Krebs-bicarbonate Ringer solution; PD, potential difference; SCC, short-circuit current; R, resistance; I, current; U, voltage; LLOQ, lower limit of quantitation; LC/MS, liquid chromatography/mass spectrometry.
- Received May 23, 2006.
- Accepted August 10, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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