Xenobiotic metabolism and enzyme induction in isolated rat intestinal microsomes.
Intestinal microsomes were isolated from rats pretreated with 3-methylcholanthrene (MC), phenobarbital (PB), and pregnenolone-16alpha-carbonitrile (PCN). The metabolism of benzo[a]pyrene (BP), 7-ethoxyresorufin, 7-ethoxycoumarin, and biphenyl were examined. MC induces a 30-fold increase in BP metabolism. With control microsomes, BP metabolism is inhibited by metyrapone, SKF 525-A, and antimycin A, but is stimulated 4.5-fold by rotenone. With microsomes from MC-treated rats, BP metabolism is inhibited by metyrapone, SKF 525-A, antimycin A, and rotenone. MC pretreatment increases 7-ethoxyresorufin de-ethylase by almost 20-fold and ethoxycoumarin de-ethylase by almost 18 fold. PB pretreatment produces less than a 2-fold increase in both de-ethylases. PCN pretreatment inhibits 7-ethoxyresorufin and 7-ethoxycoumarin de-ethylases. In rats fasted for 2 days, neither de-ethylase could be detected in intestinal microsomes. Biphenyl 2- and 4-hydroxylase activities were induced less than 4-fold by MC or PB pretreatment.
D000818:Animals; D001579:Benzopyrene Hydroxylase / Q000378:metabolism; D001580:Benzopyrenes / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D066298:In Vitro Techniques; D007422:Intestines / Q000648:ultrastructure*; D008297:Male; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D051381:Rats
D001580:Benzopyrenes; D004364:Pharmaceutical Preparations; D006899:Mixed Function Oxygenases; D001579:Benzopyrene Hydroxylase