细胞色素P450scc在人早期胎盘中的表达（简报）

人妊娠期间,胎盘合成大量的类固醇激素,与妊娠的启动、维持、分娩以及胎儿的发育均存在密切的关系。阐明胎盘类固醇激素特别是孕酮合成与分泌的调节机制对于寻找理想的生育调控技术和生殖保健方法具有重要的意义。因此,胎盘类固醇激素合成与分泌的调节向来是生殖生物学与妇产科学领域所关注的焦点问题之一,     

文昌鱼生殖内分泌生理学研究进展

近１０多年来,文昌鱼生殖内分泌生理学研究取得新进展,先后发现了文昌鱼脑泡和哈氏窝能够合成类似哺乳动物和鱼类促性腺激素,文昌鱼体内存在ＬＨ－ＲＨ、性腺组织能够合成性类固醇激素,以及在文昌鱼神经系统存在多种与调节生殖活动有关的神经递质,表明文昌鱼开始建立了类似脊椎动物,原始的生殖激素调控系统。     

抑制素的生理作用

抑制素是近年来提纯的一种主要由性腺分泌的糖蛋白激素,其主要作用是抑制腺垂体分泌泡刺激素、胎盘激素、胎盘激素的分泌、对生殖细胞的发育成熟及生殖活动都有一定的影响。     

内分泌细胞中溶酶体对激素分泌调节的作用

本实验用外源性雄激素引起垂体促性腺激素细胞和睾丸间质细胞分泌抑制,对这两种细胞中的溶酶体及分泌吞噬和自体吞噬活动进行了超微结构形态观察和半定量分析。实验中应用了CMP酶细胞化学技术和免疫胶体金技术。研究结果显示,在分泌受抑制状态下,垂体促性腺激素细胞中溶酶体增多,分泌吞噬活动加强;与此同时,睾丸间质细胞也表现溶酶体增多、自体吞噬活动加强。这些结果不仅再次证明在分泌蛋白质激素细胞中溶酶体以分泌吞噬的方式参与了激素分泌调节,更重要的是初步证明在分泌类固醇激素细胞的分泌调节中,也有溶酶体的参与,其形式是自体吞噬作用。细胞通过自体吞噬作用得以在短时间内清除一部分合成激素的细胞器和其中的激素,这可能是分泌类固醇激素的细胞及时有效地调整激素分泌量的一项重要机制,与分泌蛋白质激素细胞的分泌吞噬有着相同的意义。     

黄体类固醇激素受体的结构功能及其生理调节

在哺乳动物中,黄体的主要功能是合成并分泌孕酮,同时还合成适量的雌二醇。孕酮不但是发情周期长短的主要调节因子,而且也为胚胎植入与发育创造合适条件。这些类固醇激素通过特异性核受体对其靶细胞发挥作用,这些受体又属于受体依赖性转录因子家族。其中,孕酮是通过其核受体亚型A或B对靶细胞发挥生理功能,而雌二醇是通过其α或β受体对靶细胞发挥生理功能。另外,这些类固醇激素还可以通过细胞膜上类固醇激素结合蛋白,迅速激活胞内信号通路发挥功能,包括孕酮膜受体组分1和2、孕酮膜受体α、β和γ,以及G蛋白偶联的雌二醇受体。该文通过阐述黄体类固醇激素受体的分子结构、生理功能及其调节机制,旨在进一步理解类固醇激素受体在黄体生理功能调节中的重要作用。     

季节性变化对雌性恒河猴生殖功能的影响

目的　研究季节性变化对雌性恒河猴生殖功能的影响。方法　采用随机抽样法和放射免疫测定法 ,分析了不同时期雌性恒河猴性皮肤变化、月经周期和生殖激素变化的特点。结果　 ( 1)性征的季节性变化 :在生殖季节雌性恒河猴几乎都出现性皮肤反应 ,出现比较规则月经周期 ,在非生殖季节只有部分雌性恒河猴出现性皮肤反应 ,月经周期不规则 ,行经频率低 ,有的出现长时间的闭经 ;( 2 )生殖激素的季节性变化 :在生殖季节促性腺激素和性类固醇激素的分泌水平都出现周期性的变化 ,而非生殖季节促性腺激素和性类固醇激素的分泌水平没有显著的差异。结论　雌性恒河猴性皮肤变化、月经周期和生殖激素存在明显的季节性差异 ,这种差异导致了雌性恒河猴生殖功能的季节性变化     

鱼类促性腺激素分泌的调节机理和高效新型鱼类催产剂

鱼类和其他脊椎动物一样,由下丘脑—脑垂体—性腺轴调节整个生殖活动,其中由脑垂体合成与分泌的促性腺激素(GtH)起着十分重要的作用。在一定环境条件影响和下丘脑的调控作用支配下,使脑垂体GtH的合成与释放活动增强,它作用于性腺组织而诱导性类固醇激素的产生,进而促使配子发育成熟和排精与排卵。因此,长期以来都是使用外源的GtH,如鲤鱼(或其他鱼类)脑垂体匀浆液或粗提的人体绒毛膜促性腺激素(HCG)作为鱼类人工繁殖的催产剂。这些催产剂虽有较好效果,但来源有限,成本高,亲鱼易产生抗药性,催产后死亡     

昆虫变态的激素与基因调控

昆虫变态是一个有趣而复杂的生物学现象,有不完全变态和完全变态。昆虫通过变态获得飞翔与生殖能力,扩大了生活范围,增强了适应能力。昆虫变态主要由咽侧体分泌的保幼激素和前胸腺分泌的蜕皮激素协同调控,众多基因参与。本文综合近几年的研究进展,重点介绍昆虫变态过程中保幼激素与蜕皮激素通过级联反应基因和microRNA调控的机制,以及保幼激素和蜕皮激素的合成调节机制。     

类固醇和脑功能的研究进展

在性腺、肾上腺及胎盘组织中合成的类固醇激素对于人体的生长发育及各种生理代谢功能具有非常重要的作用,其中对脑功能的调节越来越受到人们的关注,尤其近年来发现脑组织自身能从头合成几乎全部的类固醇激素,意味着脑源性的和外周源性的类固醇激素相互协调,相互为用,共同调控着脑的生理和病理变化,如在学习和记忆、突触的传递功能、神经保护、神经退行性病变（尤其Alzheimer’s病）、情绪、应激以及月经相关疾病中起着非常重要的作用。本文就这些方面做一综述。     

子宫珠蛋白的结构与功能

子宫珠蛋白(UG)是类固醇激素诱导的、进化保守的多功能蛋白,从其基因结构、蛋白质结构、分布调节、合成的机制及其功能等方面来看,UG通过其假定受体介导自分泌和旁分泌途径发挥作用,它可能属于细胞因子/趋化因子家族,关于UG结构、调节和功能的阐明将为揭示人类一般疾病、探索胚胎植入奥秘以及研究肿瘤发生机制提供新的认识.     

Oxidized adrenodoxin acts as a competitive inhibitor of cytochrome P450scc in mitochondria from the human placenta.

The conversion of cholesterol to pregnenolone by cytochrome P450scc is the rate-determining step in placental progesterone synthesis. The limiting component for placental cytochrome P450scc activity is the concentration of adrenodoxin reductase in the mitochondria, where it permits cytochrome P450scc to work at only 16% of maximum velocity. Adrenodoxin reductase serves to reduce adrenodoxin as part of the electron transfer from NADPH to cytochrome P450scc. We therefore measured the proportion of adrenodoxin in the reduced form in intact mitochondria from the human placenta during active pregnenolone synthesis, using EPR. We found that the adrenodoxin pool was only 30% reduced, indicating that the adrenodoxin reductase concentration was insufficient to maintain the adrenodoxin in the fully reduced state. As both oxidized and reduced adrenodoxin can bind to cytochrome P450scc we tested the ability of oxidized adrenodoxin to act as a competitive inhibitor of pregnenolone synthesis. This was done in a fully reconstituted system comprising 0.3% Tween 20 and purified proteins, and in a partially reconstituted system comprising submitochondrial particles, purified adrenodoxin and adrenodoxin reductase. We found that oxidized adrenodoxin is an effective competitive inhibitor of placental cytochrome P450scc with a Ki value half that of the Km for reduced adrenodoxin. We conclude that the limiting concentration of adrenodoxin reductase present in placental mitochondria has a two-fold effect on cytochrome P450scc activity. It limits the amount of reduced adrenodoxin that is available to donate electrons to cytochrome P450scc and the oxidized adrenodoxin that remains, competitively inhibits the cytochrome.     

Placental cytochrome P450scc (CYP11A1): comparison of catalytic properties between conditions of limiting and saturating adrenodoxin reductase

The mitochondrial side-chain cleavage of cholesterol, catalysed by cytochrome P450scc, is rate-limiting in the synthesis of progesterone by the human placenta. Cytochrome P450scc activity is in turn limited by the concentration of adrenodoxin reductase (AR) in placental mitochondria. In order to better understand which components of the cholesterol side-chain cleavage system are important in the regulation of placental progesterone synthesis, we have examined their effects on P450scc activity with both saturating and limiting concentrations of AR. The present study reveals that decreasing the AR concentration causes a decrease in the K(m) of cytochrome P450scc for cholesterol, facilitating saturation of the enzyme with its substrate. Decreasing AR resulted in P450scc activity becoming less sensitive to changes in P450scc concentration. The adrenodoxin (Adx) concentration in mitochondria from term placentae is near-saturating for P450scc and under these conditions, we found that decreasing AR reduces the K(m) of P450scc for adrenodoxin. Increasing either the cholesterol or P450scc concentration increased the amount of AR required for P450scc to work at half its maximum velocity. A relatively small increase in AR can support considerably higher rates of side-chain cleavage activity when there is a coordinate increase in AR and P450scc concentrations. We conclude from this study that cholesterol is near-saturating for cytochrome P450scc activity in placental mitochondria due to the P450scc displaying a low K(m) for cholesterol resulting from the low and rate-limiting concentration of AR present. This study reveals that it is unlikely that cholesterol or adrenodoxin concentrations are important regulators of placental progesterone synthesis but AR or coordinate changes in AR and P450scc concentrations are likely to be important in its regulation.     

The concentration of adrenodoxin reductase limits cytochrome p450scc activity in the human placenta.

We have previously reported that cytochrome P450scc activity in the human placenta is limited by the supply of electrons to the P450scc [Tuckey, R. C., Woods, S. T. & Tajbakhsh, M. (1997) Eur. J. Biochem. 244, 835-839]. The aim of the present study was to determine whether it is adrenodoxin reductase, adrenodoxin or both which limits cytochrome P450scc activity and hence progesterone synthesis in the placenta. We found that the concentrations of adrenodoxin reductase and adrenodoxin in placental mitochondria were both considerably lower than the concentrations of these proteins in the bovine adrenal cortex. When P450scc activity assays were carried out at high mitochondrial protein concentrations, we found that the addition of exogenous adrenodoxin reductase to sonicated mitochondria rescued pregnenolone synthesis to a level above that for intact mitochondria, showing that adrenodoxin is near-saturating in vivo. In contrast, pregnenolone synthesis by sonicated mitochondria was almost zero even after the addition of human adrenodoxin. This shows that the concentration of endogenous adrenodoxin reductase was insufficient to support appreciable rates of pregnenolone synthesis, even when concentrated mitochondrial samples were used. Comparative studies with human and bovine adrenodoxin reductase have revealed that a twofold higher concentration of human adrenodoxin reductase is required for maximal P450scc activity in the presence of saturating human adrenodoxin. Thus, not only is the adrenodoxin concentration low in placental mitochondria, but the amount required for maximal P450scc activity is higher than that for the bovine reductase. Overall, the data indicate that the adrenodoxin reductase concentration limits the activity of P450scc in placental mitochondria and hence determines the rate of progesterone synthesis.     

Cholesterol-hydroxylating cytochrome P-450 from bovine adrenal cortex mitochondria and human placenta: immunochemical properties and structural characteristics

An immunochemical comparison of components of cholesterol side chain cleavage system from bovine adrenocortical and human placental mitochondria has been carried out. Antibodies against cytochrome P-450scc, adrenodoxin reductase and adrenodoxin from bovine adrenocortical mitochondria were shown to cross-react with corresponding antigens of human placental mitochondria. A highly sensitive immunochemical method for cytochrome P-450scc determination has been developed. Limited proteolysis of cytochrome P-450scc of human placental mitochondria was studied, and the products of trypsinolysis were identified using antibodies against cytochrome P-450scc and fragments of its polypeptide chain: F1, F2 and F3. Immunochemical relatedness of ferredoxins from bovine adrenocortical and human placental mitochondria allowed one to develop a fast and efficient method for cytochrome P-450scc purification from human placental mitochondria by affinity chromatography on adrenodoxin-Sepharose.