Mechanisms for the release and redistribution of 2,4,5,2',4',5'-hexachlorobiphenyl (6-CB) from hepatic tissues in the rat.
The translocation of 6-[14C]CB from rat hepatic tissues to various media was studied employing in situ hepatic perfusion and primary hepatocyte culture techniques. 6-[14C]CB release from the hepatic tissues of female rats pretreated with 2 microCI 6-CB was dependent on the relative proportion of perfusate buffer components. Approximately 10% of hepatic 6-CB was released into buffer containing either 4% BSA or 4% BSA and 100 mg/dl exogenous human very low density lipoproteins (VLDL). 6-CB release was significantly increased under simulated hyperlipidemic conditions (400 mg VLDL/dl). Release declined when BSA was eliminated or replaced with Dextran. The distribution of 6-CB between the triacylglycerol (TG)-rich VLDL and the protein buffer components was found to be dependent on the ratio of TG:protein. Under hyperlipidemic perfusate conditions, approximately 83% of the 6-CB associated with the BSA fraction. Under normolipidemic conditions, 99% of the 6-CB associated with BSA. The concentration of 6-CB in TG was greatly increased under hyperlipidemic conditions. Thus, 6-CB distribution under simulated normolipidemic conditions could not be explained by saturation of the VLDL fraction. Approximately 15% of 6-CB was released from hepatocytes prepared from late pregnant or age-matched control rats. Eighty percent of 6-CB was associated with VLDL secreted from hepatocytes. The TG:protein ratio in culture media was approximately 1: 6 while ratios of 1:20 or 1:600 occurred in the perfusion studies. These data suggest that 6-CB may be released from hepatic tissues in association with newly synthesized TG, but that once in the circulation, its distribution is dependent on the ratio of TG to protein present.
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D008079:Lipoproteins, VLDL / Q000096:biosynthesis; D008099:Liver / Q000378:metabolism*; D010477:Perfusion; D011078:Polychlorinated Biphenyls / Q000378:metabolism*; D011247:Pregnancy; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution; D014280:Triglycerides / Q000378:metabolism
D008079:Lipoproteins, VLDL; D011506:Proteins; D014280:Triglycerides; D011078:Polychlorinated Biphenyls; C014024:2,4,5,2',4',5'-hexachlorobiphenyl