Utilization of cultured chick embryo hepatocytes as in vitro bioassays for polychlorinated biphenyls (PCBs): Quantitative structure-induction relationships

The concentration-dependent induction of aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin-O-deethylase (EROD) activities by several PCB congeners was determined in primary chick embryo hepatocytes in culture. The most active inducers were the coplanar PCBs, 3,3′,4,4′-tetra- and 3,3′,4,4′5-pentachlorobiphenyl (pentaCB) with EC₅₀ values of 1.2 × 10^-9 and 1.5 × 10^-9 M (AHH induction) and 2.3 × 10^-9 and 1.2 × 10^-9 M (EROD induction) respectively. The corresponding EC₅₀ values for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were 2.4 × 10^-11 and 7.2 × 10^-11 M for AHH and EROD induction respectively. Three monoortho coplanar PCB analogs, 2,3,3′,4,4′-pentaCB, 2,3′,4,4′,5-pentaCB and 2,3,3′,4,4′,5-hexaCB also exhibited induction activity but their corresponding EC₅₀ values were much higher than observed for the coplanar PCBs. Several di- and triortho-substituted PCB congeners were weakly active as inducers of AHH and EROD activity. The structure-induction relationships for the coplanar and monoortho coplanar PCBs in the chick embryo hepatocytes were comparable to those previously reported in rat hepatoma H-4-II E cells and in in vivo studies.