Effects of 3-methylsulphonyl-4,5,3',4',-tetrachlorobiphenyl and 7,8-benzoflavone on aryl hydrocarbon hydroxylase activities of murine hepatic microsomes prepared from inbred strains with different Ah responsiveness.

In this work, we employed three Ah nonresponsive strains of mice, AKR, DBA and DDD, and three Ah responsive ones, C57, BALB and C3H, and prepared hepatic microsomes after the treatment of 3-methylcholanthrene (MC; 42 mg/kg, once) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 20 micrograms/kg, 6 times) in order to investigate the effect of 3-methylsulphonyl-4,5,3',4'-tetrachlorobiphenyl (3-MSF-4,5,3',4'-TCB; 1.5-45 micrograms/ml) and 7,8-benzoflavone (ANF; 1.4-42 micrograms/ml) on the hepatic microsomal AHH activities and the following results were obtained. 1. In the Ah nonresponsive strains of mice, 70 and 20% of the induced AHH activities with MC and TCDD, respectively, were attributable to the basal control enzyme activity and in the Ah responsive ones, only 4.2 and 1.4% of the induced activities with the two chemicals to the untreated control one, respectively. 2. 3-MSF-4,5,3',4'-TCB and ANF enhanced or reduced the enzyme activity depending on both their concentrations and kinds of microsomes employed, namely, control-, MC- and TCDD-microsomes. ANF showed higher potency for both the activation and inhibition of the AHH activity than 3-MSF-4,5,3',4'-TCB. 3. The effects of 3-MSF-4,5,3',4'-TCB and ANF on the enzyme activity of the MC treated Ah nonresponsive mice and those of the untreated control Ah responsive animals were quite similar and their effects on the AHH activity of the TCDD treated Ah nonresponsive strains were also almost the same as those of the MC or TCDD treated Ah responsive ones.(ABSTRACT TRUNCATED AT 250 WORDS)