Dietary absorption efficiencies and toxicokinetics of polychlorinated biphenyls in ring doves following exposure to Aroclor® mixtures

Ring doves (Streptotpelia risoria) were fed a meal of pellets spiked with an Aroclor(R) mixture. Feces were collected from birds after fasting 31 h postexposure and dietary absorption efficiencies (AbE) of polychlorinated biphenyls (PCBs) were determined by mass balance. Polychlorinated biphenyl AbEs ranged from 0.86 to 0.97 for individual congeners and were similar to the lipid AbE of 0.90. The AbEs exhibited a declining trend with increasing chemical hydrophobicity. The toxicokinetics of PCBs and dietary lipids in blood plasma were also followed in the exposed birds for 25 h after feeding the contaminated meal. Despite decreasing trends in net AbEs with increasing chemical hydrophobicity, all PCBs exhibited similar blood toxicokinetics as observed for dietary lipids. The PCB plasma uptake rate constants exhibited a positive correlation with chemical hydrophobicity such that the most hydrophobic congener PCB 180 approached the plasma uptake rate constant measured for dietary lipids. Trends in assimilation kinetics of PCBs in blood were not consistent with the general prediction that solubility limitations of chemicals in the unstirred water layer (UWL) contribute to declines in net AbEs for highly hydrophobic chemicals. The data are consistent with a micelle-mediated diffusion model, which indicates that dietary lipids and hydrophobic contaminants can cross the UWL and enter intestinal tissues at equivalent rates; however, solubility limitations of highly hydrophobic chemicals in mixed micelles may contribute to decline in net AbEs.