Determination of the binding of 2,4,5,2',4',5'-hexachlorobiphenyl by low density lipoprotein and bovine serum albumin.

The mechanism of transport of polychlorinated biphenyls (PCBs) to and from peripheral cells is not known. Plasma proteins, which bind a variety of compounds including hydrophobic molecules, are most likely to be involved in PCB transport. In order to study the role of lipoproteins in the transport and distribution of PCBs to cells, an assessment of the nature and extent of the interaction and binding of PCBs to plasma proteins is necessary. In this report a simple filter assay procedure for the analysis of binding of 2,4,5,2',4',5'-hexachlorobiphenyl (HCB) by low density lipoproteins and serum albumin is described. The method allowed compete recovery of the PCBs, and reduced errors due to nonspecific binding to the apparatus to insignificant values. Low density lipoprotein bound HCB at several noninteractive sites (number of binding sites n = 30; binding constant K = 2.7 x 10(5); dissociation constant Kd = 7.2 x 10(-6) M). Bovine serum albumin bound HCB at one noninteractive site (n = 0.53; K = 5.1 x 10(5); Kd = 1.9 x 10(-6) M). The results indicate that albumin and low density lipoprotein bind HCB effectively and suggest that plasma proteins may play a role in its distribution to peripheral cells.