title: Estrogen-binding sites in the liver of sexually mature male and female brown trout, Salmo trutta L.
abstract: Binding sites with characteristics conforming to those of a putative estrogen receptor have been identified in the liver of sexually mature male and female brown trout. [3H]Estradiol is bound with high affinity (kD in the 10(-9) M range) and limited capacity (less than 400 fmol mg-1 protein) to a proteinaceous moiety in liver cytosol. Binding is highly specific, only estradiol and estrone displace specifically bound [3H]estradiol. Cortisol, testosterone, 11-ketotestosterone, and 17 alpha, 20 beta-dihydroxyprogesterone are inactive. Labeled cytosol is retained on DNA-cellulose columns, eluting with 0.1 M NaCl. The liver of a sexually mature female brown trout contains more than twice as many binding sites as that of the male (168 +/- 15 fmol mg-1 protein cf. 69 +/- 4 fmol mg-1 protein), and no difference in kD is observed between males and females (2.6 +/- 0.2 10(-9) M and 2.9 +/- 0.3 10(-9) M, respectively). Plasma from both male and female brown trout was also found to bind [3H]estradiol, but with lower affinity (kD in 10(-8) M range) and higher capacity (4000-11,000 fmol mg-1 protein) and with less specificity. Estradiol, testosterone, and 11-ketotestosterone all displaced plasma-bound [3H]estradiol. It is concluded that cytosol and plasma binding of estradiol in brown trout are distinct, and indicative of the presence of an intracellular hepatic estrogen receptor and a plasma sex-steroid-binding protein.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002846:Chromatography, Affinity; D003600:Cytosol / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism; D004970:Estrone / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000494:pharmacology; D011960:Receptors, Estrogen / Q000378:metabolism*; D012487:Salmonidae / Q000378:metabolism*; D012737:Sex Factors; D012741:Sexual Maturation; D014337:Trout / Q000378:metabolism*
chemical_list: D011960:Receptors, Estrogen; D004970:Estrone; D004958:Estradiol; D010447:Peptide Hydrolases