Kloas W, Schrag B, Ehnes C, Segner H
Department of Inland Fisheries, Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, D-12587 Berlin, Germany.
Gen Comp Endocrinol. 2000 Sep;119(3):287-99. doi: 10.1006/gcen.2000.7521.
Competitive receptor binding assays have been suggested as an in vitro screening tool for assessing the activity of alleged estrogenic substances. In this study, we determined the ability of steroidal and nonsteroidal substances to inhibit the binding of [(3)H]17 beta-estradiol (E2) to the hepatic estrogen receptor (ER) and the plasma sex steroid binding protein (SBP) of the teleost fish, the common carp (Cyprinus carpio). The objectives of the study were (1) to characterize ER binding in the liver cytosol of male and female carp, (2) to establish complete [(3)H]E2 displacement curves from carp ER for a range of natural and xenobiotic substances and to compare the ligand data of carp ER with published data from other vertebrate species to reveal possible species differences, and (3) to determine the interaction of natural and xenobiotic substances with the steroid binding site of SBP in carp plasma. The results indicate the presence of a single class of estrogen binding sites with high affinity and limited capacity in liver cytosol of carp. The various test agents showed partly quantitative differences in their binding affinities, with the xenobiotics generally showing limited ability to displace [(3)H]E2 from the hepatic ER or from plasma SBP of carp. However, we found no evidence that a compound is an ER ligand exclusively in one species. The findings of this study indicate that interspecies extrapolation of steroid receptor binding data is possible on a yes/no basis but not on a quantitative basis.
竞争性受体结合试验已被提议作为一种体外筛选工具，用于评估所谓雌激素物质的活性。在本研究中，我们测定了甾体和非甾体物质抑制[³H]17β-雌二醇（E2）与硬骨鱼鲤鱼（Cyprinus carpio）肝脏雌激素受体（ER）及血浆性类固醇结合蛋白（SBP）结合的能力。本研究的目的是：（1）表征雌雄鲤鱼肝脏胞质溶胶中的ER结合情况；（2）针对一系列天然和外源性物质建立鲤鱼ER的完整[³H]E2置换曲线，并将鲤鱼ER的配体数据与其他脊椎动物物种已发表的数据进行比较，以揭示可能的物种差异；（3）确定天然和外源性物质与鲤鱼血浆中SBP的类固醇结合位点之间的相互作用。结果表明，鲤鱼肝脏胞质溶胶中存在一类具有高亲和力和有限容量的单一雌激素结合位点。各种测试剂在结合亲和力上表现出部分定量差异，外源性物质通常显示出从鲤鱼肝脏ER或血浆SBP置换[³H]E2的能力有限。然而，我们没有发现证据表明一种化合物仅在一个物种中是ER配体。本研究结果表明，类固醇受体结合数据的种间外推在“是/否”的基础上是可行的，但在定量基础上不可行。
