title: Inhibition of dexamethasone binding to human glucocorticoid receptor by New World primate cell extracts.
abstract: To determine if New World primates express an inhibitor that influences glucocorticoid receptor (GR) binding characteristics, we examined [3H]dexamethasone binding in cytosol prepared from B95-8 lymphoid cells, derived from the cotton top tamarin (Saguinus oedipus), in combination with cytosol prepared from human or rat tissues. B95-8 cytosol inhibited specific binding of [3H]dexamethasone (P < 0.01) when mixed with cytosol prepared from either a human lymphoid cell line (HL) or rat thymus. The inhibitory activity was heat labile and trypsin sensitive. Peak inhibitory activity was found in the 150-200 kd fractions after Sephacryl G-200 ultrafiltration. Scatchard analysis of [3H]dexamethasone binding using mixed cytosol showed a diminished GR apparent binding affinity when compared to HL cytosol. Kinetic studies using mixed cytosol indicated that B95-8 cytosol did not affect the apparent dissociation rate of [3H]dexamethasone. These data demonstrate that B95-8 cells contain a competitive inhibitor that prevents binding of dexamethasone to its cognate receptor.
mesh_terms: D000818:Animals; D002460:Cell Line; D002850:Chromatography, Gel; D003600:Cytosol / Q000737:chemistry*; D003907:Dexamethasone / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000737:chemistry*; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism*; D012452:Saguinus; D014316:Tritium; D014357:Trypsin / Q000494:pharmacology
chemical_list: D011965:Receptors, Glucocorticoid; D014316:Tritium; D003907:Dexamethasone; D014357:Trypsin