title: High-affinity binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin in cell nuclei from rat liver.
abstract: The intranuclear binding of radioactive 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rat liver has been studied both in vivo and in vitro. Following the intravenous administration of [1,6-3H]TCDD, a maximum uptake by cell nuclei could be observed at 2 h after injection with a concurrent decrease in the cytosolic uptake. Using linear sucrose density gradient centrifugation, dextran-coated charcoal adsorption assay, DEAE-Sepharose ion-exchange chromatography, competition, enzymatic and saturation studies, a high-affinity binding protein for TCDD in liver cell nuclei could be demonstrated both in vivo and after an exchange in vitro of intravenously administered unlabelled 2,3,7,8- tetrachlorodibenzofuran (TCDBF) for [3H]TCDD. Sucrose density gradient analysis showed a size of 4-5 S for both the cytosolic and nuclear TCDD binding entity. The specific binding of [3H]TCDD to nuclear components was heat labile and saturable and had an equilibrium dissociation constant of 1.05 nM. Based on a differential susceptibility to specific hydrolases, i.e. DNAase, RNAase, trypsin and pronase, the binding entity appears to be a 4-5 S salt-extractable protein.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002467:Cell Nucleus / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D003850:Deoxyribonuclease I; D003851:Deoxyribonucleases / Q000378:metabolism; D004147:Dioxins / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012259:Ribonuclease, Pancreatic; D012260:Ribonucleases / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D004147:Dioxins; D000072317:Polychlorinated Dibenzodioxins; D003851:Deoxyribonucleases; D004720:Endonucleases; D012260:Ribonucleases; D003850:Deoxyribonuclease I; D012259:Ribonuclease, Pancreatic