Interactions of diethylstilbestrol (DES) and DES analogs with membrane progestin receptor-alpha and the correlation with their nongenomic progestin activities.
Progestin induction of oocyte maturation (OM) in fish is a useful model for investigating endocrine disruption of nongenomic steroid actions. Although diethylstilbestrol (DES) analogs have been shown to mimic the actions of progestins to induce meiotic maturation of goldfish and zebrafish oocytes, their molecular mechanisms of action remain unclear. The ability of these endocrine-disrupting chemicals (EDCs) to interact with the progestin receptor mediating OM was investigated in receptor binding assays using plasma membranes from goldfish ovaries and breast cancer cells transfected with goldfish membrane progestin receptor (mPR)-alpha. Membranes prepared from both ovaries and mPRalpha-transfected cells showed high-affinity, saturable, displaceable, single binding sites specific for the goldfish maturation-inducing steroid, 17alpha,20beta-dihydroxy-4-pregnen-3-one (17,20beta-DHP). DES and DES analogs (dipropionate-DES and hexestrol), which induce OM in goldfish, bound to the receptor and caused concentration-dependent displacement of [3H]-17,20beta-DHP, whereas dimethyl ether-DES had no affinity for the receptor. Scatchard plot analysis of specific 17,20beta-DHP binding in the presence of different amounts of DES showed that DES binding is of the noncompetitive type. The activities of DES and DES analogs to induce meiotic maturation of goldfish oocytes were examined in an in vitro bioassay. Whereas a concentration-dependent induction of OM was observed in response to DES, dipropionate-DES, and hexestrol, dimethyl ether-DES did not show any OM-inducing activity. The close correspondence between binding of DES and its analogs to the mPRalpha protein and their OM-inducing activities suggests a mechanism of endocrine disruption mediated by binding to mPRalpha resulting in its activation, thereby mimicking the nongenomic action of the progestin 17,20beta-DHP.
Tokumoto
Toshinobu
T
Department of Biology, Faculty of Science, National University Corporation Shizuoka University, Shizuoka 422-8529, Japan. sbttoku@ipc.shizuoka.ac.jp
Tokumoto
Mika
M
Thomas
Peter
P
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004054:Diethylstilbestrol / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D006054:Goldfish / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D015394:Molecular Structure; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010053:Ovary / Q000378:metabolism; D011372:Progestins / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D011980:Receptors, Progesterone / Q000235:genetics / Q000378:metabolism*; D013256:Steroids / Q000378:metabolism; D013629:Tamoxifen / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology
D008565:Membrane Proteins; D011372:Progestins; D011980:Receptors, Progesterone; D013256:Steroids; D013629:Tamoxifen; D004054:Diethylstilbestrol