The cytosolic receptor binding affinities and ahh induction potencies of 29 polynuclear aromatic hydrocarbons

The dose-response rat hepatic cytosolic receptor-binding avidities, aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) induction potencies in rat hepatoma H-4-II E cells in culture were determined for 29 polynuclear aromatic hydrocarbons. It was apparent that the magnitude of the EC₅₀ values for these in vitro responses were strongly dependent on structure. Dibenz[a,h]anthracene (1.6 × 10^-8 M), 7-methylbenz[a]anthracene (1.6 × 10^-8 M), 3-methylcholanthrene (2.8 × 10^-8 M) and picene (4.5 × 10^-8 m) exhibited the highest affinity for the receptor protein and these compounds were only 5-fold less active the 2,3,7,8-tetrachlorodibenzo-p-dioxin (1 × 10 ^-8 M). All of the compounds which were active in the receptor-binding and monooxygenase enzyme-induction assays possessed one common structural feature, namely the presence of a phenanthrene structure fused with at least 1 benzo ring. The results also demonstrated that there was not any apparent correlation between the receptor-binding avidities and in vitro monooxygenase enzyme-induction potencies for the most active polynuclear aromatic hydrocarbons.