title: A high-affinity oestrogen-binding protein in cockerel liver cytosol.
abstract: In contrast with several earlier reports, cytosol from cockerel liver contains a significant concentration of a protein that binds oestradiol with high affinity. To demonstrate the activity, certain alterations in the conventional method of preparation of cytosol must be made. Homogenization in sucrose-containing buffer at pH 8.4 in the presence of proteinase inhibitors and rapid fractionation of the cytosol with (NH4)2SO4 enables demonstration of a single class of oestradiol-binding sites with a Kd of about 1 nM and specificity only for oestrogens. The concentration is about 300 sites per cell in liver from 2-week-old cockerels. Oestradiol treatment in vivo decreases the number of exchangeable cytosol oestradiol-binding sites by about 80% for 1--4h, after which time it is gradually restored. Gel filtration of the cytosol preparation in the presence of high salt concentrations reveals that most of the oestradiol-binding activity is in high-molecular-weight aggregates, but a mild trypsin treatment generates a specific binding protein with an approximate mol.wt. of 40 000. This protein may be an oestrogen receptor.
mesh_terms: D000818:Animals; D002645:Chickens; D002850:Chromatography, Gel; D003600:Cytosol / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism* / Q000494:pharmacology; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D011485:Protein Binding; D011960:Receptors, Estrogen / Q000378:metabolism*
chemical_list: D011960:Receptors, Estrogen; D004958:Estradiol