Yamada Hideyuki, Gohyama Noriko, Honda Shin-ichiro, Hara Takayuki, Harada Nobuhiro, Oguri Kazuta
Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Toxicol Appl Pharmacol. 2002 Apr 1;180(1):1-10. doi: 10.1006/taap.2002.9366.
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.
利用缺乏芳香化酶（雌激素生物合成的关键酶）的小鼠（Ar(-/-)小鼠）研究了雌激素在肝脏Cyp2b和Cyp3a亚型表达及诱导中的作用。通过逆转录聚合酶链反应、免疫印迹以及测量睾酮6β-和16α-羟化酶活性作为标志物来确定细胞色素P450的表达。在Ar(+/+)小鼠的雌雄两性中均可见到Cyp3a11 mRNA和蛋白的基础表达。芳香化酶基因的破坏导致Cyp3a11蛋白表达增加，尽管mRNA水平保持不变。雌性特异性的Cyp3a41在Ar(-/-)小鼠中消失，并且给成年基因敲除小鼠施用外源性β-雌二醇也无法使其恢复。在破坏芳香化酶基因后，雌性特异性的Cyp2b9的组成型表达也消失了。然而，与Cyp3a41形成鲜明对比的是，一些个体的Ar(-/-)小鼠在接受外源性β-雌二醇治疗后表现出这种形式的表达。芳香化酶基因的破坏对PB介导的Cyp2b10诱导或Cyp2b9、Cyp3a11和Cyp3a41的非诱导性质没有影响。这些结果表明：（1）Cyp3a11受到雌激素的抑制；（2）雌性特异性Cyp3a41的表达是由新生儿期和/或婴儿期暴露于雌激素所编程的；（3）成年期维持雌性特异性Cyp2b9的表达需要雌激素；（4）内源性雌激素在PB诱导Cyp2b10的机制中即使有作用也很小。
