In vitro and in vivo estrogenic effects of 17alpha-estradiol in medaka (Oryzias latipes).
17alpha-Estradiol (17alpha-E2), the stereoisomer of 17beta-estradiol (17beta-E2), is considered a weak estrogen in mammals. However, little is known about its estrogenic potency in teleost fish, even though 17alpha-E2 has been frequently detected in aquatic environment. To investigate the estrogenic activity of 17alpha-E2, an in vitro assay based on the ligand-dependent interaction between medaka estrogen receptor alpha (med-ERalpha) and coactivator was conducted. Japanese medaka (Oryziaslatipes) were exposed to 1, 10, 100, 1000 and 10000ng L(-1) 17alpha-E2 (actual concentrations of 1.91, 12.81, 96.24, 1045.15, and 9320.81ng L(-1), respectively) for 3 weeks, and expression for vitellogenins (VTG-I), Choriogenin H (CHG-H) and estrogen receptor alpha (ERalpha) mRNA in the livers was analyzed by quantitative real-time RT-PCR (Q-RT-PCR). The in vitro study showed that the EC(50) of 17alpha-E2 was 114.10nM, which was 30 times less potent than that of 17beta-E2 (3.80nM). Dose-dependent induction of gene expression of VTG-I, CHG-H and ERalpha were observed. The benchmark dose (BMD) values for VTG-I, CHG-H and ERalpha were 44.16ng L(-1), 15.25ng L(-1) and 66.03ng L(-1), which were about 11-, 17- and 14-times less potent than that of 17beta-E2, respectively. Comparing this study with those reported previously in mammals, it is suggested that fish species may be more susceptive to 17alpha-E2 than mammals.
Huang
Chong
C
Peking University, Beijing, China.
Zhang
Zhaobin
Z
Wu
Shimin
S
Zhao
Yanbin
Y
Hu
Jianying
J
D000818:Animals; D004527:Egg Proteins / Q000378:metabolism; D004958:Estradiol / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D047628:Estrogen Receptor alpha / Q000378:metabolism; D004967:Estrogens / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D008099:Liver / Q000378:metabolism; D008297:Male; D009990:Oryzias / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D018675:Toxicity Tests; D014819:Vitellogenins / Q000378:metabolism
D004527:Egg Proteins; D047628:Estrogen Receptor alpha; D004967:Estrogens; D011498:Protein Precursors; D014819:Vitellogenins; C104950:choriogenin H; D004958:Estradiol