Rapid assay for oestrogen receptor binding to PCB metabolites

Hydroxylated metabolites of polychlorinated biphenyls (PCBs) bind the oestrogen receptor (ER) and increase uterine weight in animal models. This oestrogenic action of PCB metabolites is of putative human health concern. We have thus developed a system to study human in vitro PCB metabolism. Human liver microsomes produced PCB metabolites in an NADPH-dependent microsomal reaction mixture (MRM); the metabolites were tested for ER-binding affinity in the human recombinant oestrogen receptor-alpha (ER) competitive binding assay. These metabolites were identified using HPLC by comparing the retention times with known PCB-metabolites. 2,4,6-Trichlorobiphenyl (246BP) was used as a prototype to standardize this method. 246BP up to a concentration of 50 mum did not bind to ER, but 246BP-MRM competed for binding to ER; it competed for 75% of (3)H-estradiol-17beta ((3)H-E(2)) binding to ER. The ER-binding component of the 246BP-MRM had a retention time identical to that of 4'OH-246BP using HPLC. This method provides a rapid screen for the qualitative assessment of the presence of microsomally-generated ER-binding PCB metabolites to guide further characterization of these compounds by GC/MS analysis.