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  • Title: Differential induction of mRNA expression of cytochromes P450 (CYP2B1 and CYP1A1/2) by metyrapone in primary rat hepatocyte cultures.
    Author: Aubrecht J, Hirsch-Ernst KI, Foth H, Kahl GF, Höhne MW.
    Journal: Res Commun Mol Pathol Pharmacol; 1996 Oct; 94(1):47-61. PubMed ID: 8948014.
    Abstract:
    The mRNA expression of members of two cytochrome P450 (CYP) gene subfamilies involved in carcinogen activation, the CYP1A1/2 and CYP2B1 forms, was determined in primary rat hepatocyte cultures in response to metyrapone and to the inducer phenobarbital or 5,6-benzoflavone (BNF), respectively. Incubation of cells with 0.5 mM metyrapone resulted in accumulation of CYP1A1 and CYP1A2 mRNA and in a marked increase in CYP1A-associated enzymatic activity as determined by deethylation of ethoxyresorufin. Metyrapone and phenobarbital in combination acted synergistically in elevation of ethoxyresorufin O-deethylase activity. In hepatocytes treated with metyrapone or with phenobarbital, accumulation of CYP2B1 mRNA levels preceded an increase in CYP2B-associated, pentoxyresorufin O-depentylase activity. However, CYP2B1 mRNA levels were first detectable after 24 hours of treatment with phenobarbital, whereas metyrapone elicited a substantial increase in mRNA levels within 14 hours, suggesting differing mechanisms leading to accumulation of CYP2B1 mRNA under the two inducers.
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