Chakraborty C, Huet-Hudson Y M, Dey S K
Department of Obstetrics/Gynecology and Physiology, University of Kansas Medical Center, Ralph L. Smith Research Center, Kansas City 66103.
J Steroid Biochem. 1990 Jan;35(1):39-46. doi: 10.1016/0022-4731(90)90143-g.
Microsomal oestradiol-2/4-hydroxylase (OE-2/4-H) and cytosolic catechol-O-methyltransferase (COMT) (EC 2.1.1.6) activity in the uteri of pregnant and pseudopregnant rabbits during the periimplantation period were studied. The apparent Km for the 4-hydroxylation of oestradiol (3.18 microM) was considerably less than for the 2-hydroxylation reaction (13.36 microM), whereas the Vmax were almost equal. This suggests that 4-hydroxyoestradiol (4-OH-OE2) is the predominant product of OE-2/4-H in the rabbit uterus. These reactions were inhibited by SKF-525A, indicating the involvement of cytochrome P450 dependent monooxygenases. Uterine cytosolic COMT utilized 2-hydroxyestradiol (2-OH-OE2) as the preferred substrate as compared to 4-hydroxyoestradiol (4-OH-OE2). Since the rabbit uterus has a considerable capacity to synthesize 4-OH-OE2 and a lower capacity to metabolize it, it could be suggested that more 4-OH-OE2 than 2-OH-OE2 could be available to the uterus for its physiological activities. Furthermore, an increase in OE-2/4-H in Day 6 pseudopregnant and pregnant uteri with a concomitant decrease in COMT suggests the involvement of catecholoestrogens in the implantation process in the rabbit.
研究了围植入期怀孕和假孕兔子子宫中的微粒体雌二醇-2/4-羟化酶（OE-2/4-H）和胞质儿茶酚-O-甲基转移酶（COMT）（EC 2.1.1.6）活性。雌二醇4-羟化反应的表观Km（3.18 microM）远低于2-羟化反应（13.36 microM），而Vmax几乎相等。这表明4-羟基雌二醇（4-OH-OE2）是兔子子宫中OE-2/4-H的主要产物。这些反应受到SKF-525A的抑制，表明细胞色素P450依赖性单加氧酶参与其中。与4-羟基雌二醇（4-OH-OE2）相比，子宫胞质COMT优先利用2-羟基雌二醇（2-OH-OE2）作为底物。由于兔子子宫合成4-OH-OE2的能力较强，而代谢它的能力较弱，因此可以认为子宫可用于其生理活动的4-OH-OE2比2-OH-OE2更多。此外，假孕第6天和怀孕子宫中OE-2/4-H增加，同时COMT减少，这表明儿茶酚雌激素参与了兔子的植入过程。
