title: Estrogen-dependent regulation of the expression of hepatic Cyp2b and 3a isoforms: assessment using aromatase-deficient mice.
abstract: 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.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Yamada
authors.forename: Noriko
authors.initials: N
authors.lastname: Gohyama
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Honda
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hara
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Harada
authors.forename: Kazuta
authors.initials: K
authors.lastname: Oguri
mesh_terms: D000818:Animals; D001141:Aromatase / Q000172:deficiency* / Q000235:genetics; D001189:Aryl Hydrocarbon Hydroxylases; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D017931:DNA Primers / Q000737:chemistry; D004790:Enzyme Induction; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D015151:Immunoblotting; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D009929:Organ Size / Q000187:drug effects; D010089:Oxidoreductases, N-Demethylating / Q000096:biosynthesis* / Q000235:genetics; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012737:Sex Factors; D039181:Steroid 16-alpha-Hydroxylase; D014599:Uterus / Q000187:drug effects / Q000473:pathology
chemical_list: D017931:DNA Primers; D004967:Estrogens; D008565:Membrane Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D004958:Estradiol; D003577:Cytochrome P-450 Enzyme System; D001141:Aromatase; D001189:Aryl Hydrocarbon Hydroxylases; C496508:Cyp3a11 protein, mouse; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; D039181:Steroid 16-alpha-Hydroxylase; D010089:Oxidoreductases, N-Demethylating