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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

Estrogen-dependent regulation of the expression of hepatic Cyp2b and 3a isoforms: assessment using aromatase-deficient mice.

The role of estrogen in the expression and induction of hepatic Cyp2b and Cyp3a isoforms was studied using mice [ Ar (-/-) mice] lacking aromatase, a key enzyme for estrogen biosynthesis. The expression of P450s was determined by reverse transcription-polymerase chain reaction, immunoblotting, and measuring testosterone 6beta- and 16alpha-hydroxylase activity as markers. Basic expression of Cyp3a11 mRNA and protein was seen in both sexes of Ar (+/+) mice. Disruption of the aromatase gene caused an increase in the expression of Cyp3a11 protein, although the mRNA level remained unchanged. Female-specific Cyp3a41 disappeared in Ar (-/-) mice, and this could not be reversed by administration of exogenous beta-estradiol to adult knockout mice. The constitutive expression of female-specific Cyp2b9 also disappeared on disrupting the aromatase gene. However, in clear contrast to Cyp3a41, some individual Ar (-/-) mice exhibited expression of this form following treatment with exogenous beta-estradiol. Disruption of the aromatase gene had no effect on PB- mediated induction of Cyp2b10 or on the noninducible nature of Cyp2b9, Cyp3a11, and Cyp3a41. These results suggest that (1) Cyp3a11 is suppressed by estrogen; (2) the expression of female-specific Cyp3a41 is programmed by neonatal and/or infantile exposure to estrogen; (3) maintenance of the expression of female-specific Cyp2b9 requires estrogen in adults; and (4) endogenous estrogen plays little, if any, role in the mechanism by which PB induces Cyp2b10.[1]


  1. Estrogen-dependent regulation of the expression of hepatic Cyp2b and 3a isoforms: assessment using aromatase-deficient mice. Yamada, H., Gohyama, N., Honda, S., Hara, T., Harada, N., Oguri, K. Toxicol. Appl. Pharmacol. (2002) [Pubmed]
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