Influence of dietary fat on the enantioselective disposition of 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136) in female mice.

Although ingestion is the major route of exposure to polychlorinated biphenyls (PCBs), dietary factors altering their absorption and excretion are only poorly understood. In the present study, (+/-)-PCB 136 was administered orally to female C57BL/6 mice fed an unrefined (URD, 10% fat) or high fat (HFD, 40% fat) diet to investigate the effect of the dietary fat content on the disposition of PCBs. Three days after administration, PCB levels in the adipose tissue were significantly lower in HFD animals than URD animals, partly due to a higher excretion rate of PCB 136 in the HFD group. (+)-PCB 136 was enriched in all organs and in feces. In both groups, enantiomeric fractions in feces increased each day after administration. We hypothesize that low EF (enantiomeric fraction) values in feces excreted within 24h of exposure are due to the presence of undigested, racemic PCB. Higher EF values in feces excreted after two and three days are due to excretion of previously absorbed PCBs. Overall, our study suggests that the EF value may be a good tool to investigate the absorption and excretion of PCBs in vivo.

Effect of potassium perfluorooctanesulfonate, perfluorooctanoate and octanesulfonate on the phase transition of dipalmitoylphosphatidylcholine (DPPC) bilayers.

Perfluorooctanesulfonic acid (PFOS) is a persistent environmental pollutant that may cause adverse effects by inhibiting pulmonary surfactant. To gain further insights in this potential mechanism of toxicity, we investigated the interaction of PFOS potassium salt with dipalmitoylphosphatidylcholine (DPPC) - the major component of pulmonary surfactant - using steady-state fluorescence anisotropy spectroscopy and DSC (differential scanning calorimetry). In addition, we investigated the interactions of two structurally related compounds, perfluorooctanoic acid (PFOA) and octanesulfonic acid (OS) potassium salt, with DPPC. In the fluorescence experiments a linear depression of the main phase transition temperature of DPPC (T(m)) and an increased peak width was observed with increasing concentration of all three compounds, both using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate (TMA-DPH) as fluorescent probes. PFOS caused an effect on T(m) and peak width at much lower concentrations because of its increased tendency to partition onto DPPC bilayers, i.e., the partition coefficients decrease in the K(PFOS)>K(PFOA)>>K(OS). Similar to the fluorescence anisotropy measurements, all three compounds caused a linear depression in the onset of the main phase transition temperature and a significant peak broadening in the DSC experiments, with PFOS having the most pronounced effect of the peak width. The effect of PFOS and other fluorinated surfactants on DPPC in both mono- and bilayers may be one mechanism by which these compounds cause adverse biological effects.