High affinity estrogen binding by rabbit liver.
Macromolecular binding components for [3H]estradiol-17beta are present to cytosol prepared from rabbit liver. When cytosol from sexually mature male liver was incubated with [3H]estradiol and analyzed for binding on low ionic strength sucrose gradients, two peaks of binding activity were detected. One peak had a sedimentation coefficient of 4--5 S and the other had a sedimentation coefficient of 8--9 S. The two components differed from each other regarding steroid specificity and various physiocochemical parameters. [3H]estradiol binding to the 4--5 S component was not inhibited by estrogens, 5alpha-dihydrotestosterone, progesterone or cortisol. Binding to this component did not appear to be saturable and label was rapidly stripped from it by charcoal. Estradiol binding to the 8--9 S component was estrogen specific, saturable and of high affinity. The specific binder dissociates on high ionic strength sucrose gradients and sediments as a 4--5 S moiety. The specific binding protein has a Kd of 3.05 . 10(-10) M and a dissociation half-time of 33 h and there are 35.2 fmol of binding sites/mg cytosol protein. Estrogen binders are also present in liver cytosol from sexually mature female and sexually immature male rabbits. During prolonged incubation of [3H]estradiol with mature male liver cytosol at 0--5 degrees C polar metabolites of estradiol are produced.
D000818:Animals; D002606:Charcoal; D003600:Cytosol / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008970:Molecular Weight; D011402:Pronase / Q000378:metabolism; D011817:Rabbits; D011960:Receptors, Estrogen / Q000378:metabolism
D011960:Receptors, Estrogen; D002606:Charcoal; D004958:Estradiol; D003851:Deoxyribonucleases; D011402:Pronase