Received for publication December 26, 2006.
Revised February 21, 2007.
Accepted for publication March 1, 2007.

Induction of phase I and II drug metabolism in rat small intestine and colon in vitro

Abstract

The aim of this study was to evaluate drug metabolism in rat small intestinal and colon precision-cut slices during 24 h of incubation and the applicability of these slices for enzyme induction studies. Various parameters were evaluated: Intracellular levels of ATP (general viability marker), alkaline phosphatase activity (specific epithelial marker), villin expression (specific epithelial marker) and metabolic rates of 7-ethoxycoumarin (CYP1A), testosterone (CYP3A, 2B) and 7-hydroxycoumarin (glucuronide and sulphate conjugation) conversions. ATP and villin remained constant up to respectively 5 and 8 h in small intestine and up to 24 h in colon. The metabolic rate remained constant in small intestinal slices up to 8 h and decreased afterwards to 24-92%, depending on the substrate studied. The inducibility of metabolism in small intestinal and colon slices was tested with several inducers at various concentrations and incubation times. The following inducers were used: 3-methylcholanthrene, -naphthoflavone, indirubin and tert-butylhydroquinone (AhR ligands), dexamethasone (PXR/GR ligand) and phenobarbital (CAR ligand). After incubation with inducers, metabolic rates were evaluated with 7-ethoxycoumarin and testosterone (phase I), and 7-hydroxycoumarin (phase II) as substrate. All inducers elevated the metabolic rates consistent with the available published in vivo induction data. Induction of enzyme activity was already detectable after 5 h (small intestine) and after 8 h (colon) for 3-methylcholanthrene and -naphthoflavone and was clearly detectable for all tested inducers after 24 h (up to 20-fold compared with non-induced controls). In conclusion, small intestinal and colon precision-cut slices are useful for metabolism and enzyme induction studies.

Key words: CYP induction, enzyme induction, extrahepatic drug metabolism, gastrointestinal cytochrome P450, glucuronidation, phase II drug metabolism

This article has been cited by other articles:

				E. G. van de Kerkhof, I. A. M. de Graaf, A.-L. B. Ungell, and G. M. M. Groothuis Induction of Metabolism and Transport in Human Intestine: Validation of Precision-Cut Slices as a Tool to Study Induction of Drug Metabolism in Human Intestine in Vitro Drug Metab. Dispos., March 1, 2008; 36(3): 604 - 613. [Abstract] [Full Text] [PDF]