PARENT SESSION
TA5 Biodegradation and biotransformation: routes and pathways
9:00 AM to 12:30 PM, Tuesday, 08 May 2001
Session Chair: K. Solomon
Room 5

(183) Different distribution patterns for isomers and enantiomers of persistent PCB methyl sulfones in mice.

Johansson, Maria¹, Larsson, Christina², Lund, Bert-Ove¹, ^{1 2}

ABSTRACT- MeSO₂-CBs are widely found in biota. Recent studies demonstrated a strong selectivity with regard to the presence of enantiomeric MeSO₂-CBs in ringed seal blubber, polar bear adipose tissue and human liver samples. We used whole-body autoradiography to study the distribution pattern of isomeric ¹⁴C-MeSO₂-CB149 and their enantiomers in mice. All non-extracted sections were characterized by a high uptake in fat, indicating lipophilicity and persistency of isomers and enantiomers in the body. Four days post-injection, pronounced labelling of 3-MeSO₂-CB149 were found in the liver, nasal mucosa, lung bronchi, intestinal contents, and adrenal cortex whereas the radioactivity of the isomer 4-MeSO₂-CB149 was confined mainly to lung bronchi, with a lower labelling of nasal mucosa, liver, kidney and adrenal cortex. Sections extracted in organic solvents showed radioactivity from 3-MeSO₂-CB149 to be tightly bound to the nasal mucosa and intestinal contents whereas radioactivity from 4-MeSO₂-CB149 was confined to the lung bronchi and kidney cortex. The enantiomers of 3-MeSO₂-CB149 (E1 and E2), were fractionated by HPLC, and studied as above. They were both found in the nasal mucosa in extracted sections. However, E1 was also found in lung bronchi, kidney cortex and liver, whereas E2 was found in high concentrations in intestinal contents as well as in the epithelia of the appendix and of the fore and glandular stomach. The high intestinal content of E2 may imply a higher body clearance of E2 than of E1. The different distribution patterns of the enantiomers in mice indicate that enantioselective processes for MeSO₂-CB formation, uptake, transport, and body clearance may be involved. The consequences of this enantioselectivity are yet unknown, however, enantiomers of PCBs have different effects on induction of several xenobiotic-metabolizing enzymes in liver.

Key words: enantiomer, PCB methyl sulfone, distribution pattern, autoradiography