Department of Zoology, Center of Advanced Study, Banaras Hindu University, Varanasi, UP, India.
Steroids. 2010 Dec 12;75(13-14):1097-105. doi: 10.1016/j.steroids.2010.07.004. Epub 2010 Aug 11.
A radiometric assay was used to measure microsomal EH activity from tritiated H(2)O formed during the conversion of [2,4 (3)H] estradiol-17β into catecholestrogens in the microsomal fractions of liver, brain and ovary of the catfish Heteropneustes fossilis. The validation data show that enzyme activity increased with incubation time, and substrate and cofactor (NADPH) concentrations, elicited temperature optima of 30-37°C and pH optima of 6.8-7.8. EH activity was strongly NADPH-dependent and in its absence only 13.48% activity was recorded. Liver recorded the highest enzyme activity, followed by brain and ovary. EH activity showed a significant seasonal variation with the peak activity in spawning phase and the lowest activity in resting phase. In the ovary, the follicular layer (theca and granulosa) elicited the highest activity over that of the denuded oocytes. Modulatory effects of steroids on ovarian enzyme activity were further demonstrated. The incubation of postvitellogenic follicles with 1, 10 or 100 nM concentrations of various steroids for 24 h produced varied effects on EH activity. Progesterone and 2-hydroxyestradiol-17β elicited strong suppressive effects on enzyme activity. Estrogens (E(1), E(2) and E(3)) suppressed the activity in a concentration-dependent manner. Among the progestins tested, 17,20α-dihydroxy-4-pregnen-3-one, the isomer of 17,20β-dihydroxy-4-pregnen-3-one (a teleost maturation-inducing steroid) showed the lowest depressing effect. Among androgens, the testosterone metabolite 11-ketotestosterone (functional teleost androgen) showed a high suppressing effect. Corticosteroids elicited low activity with cortisol suppressed the activity at higher concentrations. The study will form a basis to understand the physiological role of catecholestrogens in ovarian functions.
采用放射性分析测定法，测量了从猫鱼（Heteropneustes fossilis）肝、脑和卵巢微粒体部分[2,4（3）H]雌二醇-17β转化为儿茶酚雌激素过程中形成的氚化 H2O 中微粒体 EH 活性。验证数据表明，酶活性随孵育时间、底物和辅助因子（NADPH）浓度的增加而增加，最适温度为 30-37°C，最适 pH 值为 6.8-7.8。EH 活性强烈依赖于 NADPH，在没有 NADPH 的情况下，仅记录到 13.48%的活性。肝脏记录的酶活性最高，其次是脑和卵巢。EH 活性表现出明显的季节性变化，产卵期活性最高，静止期活性最低。在卵巢中，卵泡层（膜和颗粒层）的活性高于裸露卵母细胞。进一步证明了类固醇对卵巢酶活性的调节作用。用 1、10 或 100 nM 浓度的各种类固醇孵育产后期卵泡 24 h 后，对 EH 活性产生了不同的影响。孕酮和 2-羟基雌二醇-17β对酶活性有强烈的抑制作用。雌激素（E1、E2 和 E3）以浓度依赖的方式抑制活性。在所测试的孕激素中，17,20α-二羟基-4-孕烯-3-酮（一种鱼类成熟诱导类固醇的异构体）的抑制作用最低。在雄激素中，睾酮代谢物 11-酮睾酮（功能性鱼类雄激素）表现出很高的抑制作用。皮质类固醇活性低，皮质醇在较高浓度下抑制活性。该研究将为理解儿茶酚雌激素在卵巢功能中的生理作用奠定基础。
