SULFUR ANALOGUES OF POLYCHLORINATED DIBENZO-p-DIOXINS, DIBENZOFURANS AND DIPHENYL ETHERS AS INDUCERS OF CYP1A1 IN MOUSE HEPATOMA CELL CULTURE AND STRUCTURE-ACTIVITY RELATIONSHIPS

Three sulfur-containing compounds, 2,3,7,8-tetrachlorothianthrene (TCTA), 2,3,7,8-tetrachlorodibenzothiophene (TCDT), and 3,3[prime],4,4[prime]-tetrachlorodiphenyl sulfide (TCDPS), were analyzed for their CYP1A1-inducing potencies--measured as aryl hydrocarbon hydroxylase (AHH) and 7-ethoxyresorufin O-deethylase (EROD) activities--in mouse hepatoma cell culture Hepa-1. Marked differences in the induction potencies were observed among the three compounds studied and between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and its sulfur analogue. The estimated EC50 values for TCDD, TCTA, and TCDT were about 8 pM, 700 pM, and 7.5 nM, respectively. TCDPS did not elicit any AHH/EROD induction. Compar…