Chlorinated trans stilbenes: Competitive binding to the ah receptor, induction of cytochrome p-450 monooxygenase activity and partial 2, 3, 7, 8-TCDD antagonism

Chlorinated trans stilbenes bind with high affinity to the cytosolic Ah receptor from Wistar rat liver. The EC₅₀values for competition with [³H]-2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) cover a range from 10–400 nM, but with no apparent relationship between molecular structure and binding activity. These compounds induce monooxygenase enzyme activity in rat hepatoma H-4-II E cells in culture only weakly, again with no apparent dependence on molecular structure, and the weakest enzyme inducers act as antagonists for the induction of these enzymes by TCDD. In vivo administration of 3, 3′, 4, 4′-tetrachloro-trans-stilbene in the rat leads to decreased Ah receptor levels.