THE BINDING PROPERTIES OF HALOGENATED BIPHENYLS TO CELLS AND MACROMOLECULES
The interaction of polychlorinated biphenyls (PCB) with serum proteins may help explain the cellular incorporation of PCB as the effect of PCB on thyroid hormone function. PCB reduces serum thyroxine and triiodothyronine levels in rats; the mechanism for this effect is unknown. The initial distribution of PCB from blood to tissue is rapid and depends on blood perfusion and tissue affinity; however, the translocation of unmetabolized PCB from its initial storage sites to adipose tissue may depend on serum and cellular protein interactions. Therefore, the ability of PCB to displace triiodothyronine binding to albumin and antibodies, as well as the effect of binding to serum proteins as a mechanism for cellular incorporation was measured.^ PCB binding to albumin showed both high and low affinity binding sites. This binding was able to prevent triiodothyronine binding to albumin. PCB and its monohydroxylated metabolites were able to displace T(,3) from specific antibody binding sites. Some of the metabolites showed a higher cross-reactivity than the parent molecule. Hydroxylation at the 4 position on the biphenyl molecule resulted in a higher cross-reactivity than hydroxylation at the 2 position with the T(,3) antibody. These experiments indicate that metabolism increases the reactivity of PCB and thus increases the possibility of specific chemical interactions with macromolecules.^ The distribution of PCB in serum showed that lipoproteins contained 94% of the total ('14)C PCB added, while 5% of the ('14)C PCB was bound to albumin. The in vitro binding of ('14)C PCB to serum obtained from rats pretreated with PCB in their diets for 6 months showed a significant decrease (p < 0.05) in binding compared to serum from untreated controls. This reduction in binding was caused by a decrease (p < 0.05) in total serum protein.^ Cellular incorporation of PCB is dependent on cell type, integrity of the plasma membrane and serum proteins. The in vitro incorporation of ('14)C PCB was higher (p < 0.05) in liver, adrenal and adipose cells than pituitary and thyroid cells. Trypsinized cells showed a significant decrease (p < 0.05) in ('14)C PCB incorporation when compared to cells isolated with collagenase, indicating that membrane integrity can affect PCB incorporation. Serum proteins can mediate the incorporation of PCB into isolated hepatocytes. Albumin, Low Density lipoprotein (LDL) and Very Low Density lipoprotein (VLDL) prevented ('14)C PCB from being incorporated into cells; whereas serum with HDL present showed a significant increase (p < 0.05) in ('14)C PCB incorporation. ^
PEPE, MICHAEL G, "THE BINDING PROPERTIES OF HALOGENATED BIPHENYLS TO CELLS AND MACROMOLECULES" (1982). ETD Collection for Fordham University. AAI8219258.