Role of lipoproteins and plasma proteins in the transport of polychlorinated biphenyls in birds

Abstract

Polychlorinated biphenyls (PCBs) are abundant industrial pollutants. Commercial mixtures contain up to 80 isomers and congeners (components), many of which accumulate by the ingestion of PCB-contaminated lipid components of food chains, and PCBs are present in the blood and adipose tissues of species at the apex of these chains, such as marine birds. We have used the pigeon as a model to investigate the transport of PCBs by plasma lipoproteins and proteins by injecting [ 14C]4-monochlorobiphenyl or [ 14C]2,2′,5,5′-tetrachlorobiphenyl and isolating the plasma fractions 24 h later. These congeners were associated both with the apoprotein and the triacylglycerol components of the plasma lipoproteins, which suggests that apoproteins may be involved in the receptor-mediated uptake of PCBs into tissues. A distinctive distribution of PCB congeners was observed 5 days after pigeons had been injected with the commercial PCB mixture Aroclor 1254. Very low density lipoproteins were associated predominantly with one congener (2,2′,4,4′,5,5′-hexachlorobiphenyl), whereas the other 40 PCBs were distributed amongst the other fractions. Hence the association between individual congeners and blood components is more complex than had been thought previously. The results indicate that the mechanisms by which ingested PCBs are transported by the blood and taken up selectively by tissues has important consequences for the way in which marine organisms respond to PCB pollution.