SCREENING ASSAY FOR DIOXIN-LIKE COMPOUNDS BASED ON COMPETITIVE-BINDING TO THE MURINE HEPATIC AH RECEPTOR .1. ASSAY DEVELOPMENT

PCDDs, PCDFs, and related analytes were assayed by binding the analyte s competitively with fixed aliquots of radiolabeled 2,3,7,8-tetrachlor odibenzo-p-dioxin (TCDD) and C57BL/6 mouse hepatic Ah receptor. Additi ve binding to the receptor was observed for a wide range of structural types of chlorinated aromatic compounds. The results of the assays we re expressed as TCDD equivalents, i.e.,the concentration of unlabeled TCDD that would give the same assay as the mixture of analytes. The de tection limit was approximately 100 pg of TCDD equivalent when the ref erence radioligand was [H-3] TCDD. The assay does not require prior kn owledge of the identities of the components of the mixture and is inte nded for use as a prescreening tool rather than as a replacement for t he conventional analysis by GC/MS.