Characterization of glucocorticoid receptors in whole and cellular subfractions of embryonic chick spinal cord.
Steroid-specific binding sites for tritiated corticosterone have been localized, via autoradiography, to motoneurons in the lateral motor columns of the adult rat spinal cord. Binding sites in adult rat spinal cord have been characterized biochemically and shown to possess the properties of a putative glucocorticoid receptor. The presence of receptors for glucocorticoids in embryonic chick spinal cord was determined and their characterization undertaken as a prelude to the study of the functions under regulation by glucocorticoids during development. Assay conditions were defined and binding of [3H]dexamethasone [( 3H]Dex) to cytosols of 6- and 10-day embryonic spinal cord and cellular subfractions of 6-day spinal cord determined. Saturable, high-affinity binding of [3H]Dex to cytosols prepared from both whole 6- and 10-day spinal cords and cells of all 3 cellular subfractions of 6-day spinal cords was observed. The binding component in 10-day cytosols was (1) proteinaceous, as binding was eliminated by heating cytosols, and (2) a macromolecular species, as it displayed a sedimentation coefficient of 8S upon centrifugation in sucrose gradients. The putative receptor displayed binding specific for glucocorticoids in a competition assay, with the exception that some inhibition of binding by the androgen ligand, methyltrienolone (R1881) was observed. The binding affinity decreased as the values for KD increased from 3.4 +/- 0.9 nM on day 6 to 15.7 +/- 1.8 nM on day 10, while the values for Bmax increased from 270 to 855 fmol/mg protein over the same period.(ABSTRACT TRUNCATED AT 250 WORDS)
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D000818:Animals; D001667:Binding, Competitive; D055598:Chemical Phenomena; D002621:Chemistry; D002642:Chick Embryo; D003600:Cytosol / Q000032:analysis; D005938:Glucocorticoids / Q000378:metabolism; D009046:Motor Neurons / Q000032:analysis*; D011869:Radioligand Assay; D011965:Receptors, Glucocorticoid / Q000032:analysis* / Q000378:metabolism; D013116:Spinal Cord / Q000032:analysis*; D013347:Subcellular Fractions / Q000032:analysis
D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid