Specific binding of polychlorinated biphenyls to rat liver cytosol protein.
Specific binding of polychlorinated biphenyls (PCBs) to rat liver cytosol protein has been detected using the 3H-labeled PCB probe 2,2',4,4',5,5'-hexachlorobiphenyl (6-CB). Binding of 6-CB to cytosol protein is displaced by its non-radioactive congener, is of high affinity (Kd approximately 3 nM) and is saturable (maximal binding capacity Bmax approximately 600 pmol/mg protein). 6-CB binding is not found in liver cytosol of animals fed a PCB-supplemented diet (500 ppm PCB for 5 days). Binding is also in vitro inhibited by high concentrations of triglyceride. PCB congeners such as 3,3',4,4',5-pentachlorobiphenyl as well as the thyroid hormones 3,5,3',5'-tetraiodothyronine and 3,5,3'-triiodothyronine (the latter hormone with an order of magnitude lower affinity) compete for the PCB binding site. On the other hand, a number of biochemically important compounds including the PCB core compound biphenyl and the hormone ligands dexamethasone and estradiol, as well as 2,3,7,8-tetrachlorodibenzo-p-dioxin, do not compete for the 6-CB binding site. The data provide the first evidence of specific binding of unmetabolized PCB congeners to distinct binding sites in rat liver cytosol.
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GSF Forschungszentrum für Umwelt und Gesundheit GmbH, Neuherberg, Germany.
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D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D011078:Polychlorinated Biphenyls / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D002352:Carrier Proteins; D011078:Polychlorinated Biphenyls; C014024:2,4,5,2',4',5'-hexachlorobiphenyl