S9 induction by the combined treatment with cyclohexanol and albendazole

Cyclohexanol (CH) is an industrial solvent capable of inducing cytochrome P 450 (CYP) enzymes including the CYP2E and CYP2B subfamilies. S9 from CH tre ated rats is able to activate several N-nitrosamines that are poorly activa ted by Aroclor 1254, phenobarbital/beta -naphthoflavone (PB/NF) or 3-methyl cholanthrene S9 fractions into mutagens detected by the Salmonella typhimur ium Ames test. Additionally, albendazole (ABZ) is a widely used anthelminti c drug and a potent inducer of the CYP1A subfamily. Since CYP1A, -2B and -2 E subfamilies are implicated in the activation of several environmental mut agens/carcinogens, we studied CYP induction in the rat liver by the combine d effect of these two compounds, and used S9 derived from it in the Salmone lla/microsome assay to compare with S9 obtained from Aroclor or PB/NF treat ed rats. Total CYP content in hepatic microsomes was induced by Aroclor, bu t not by any of the other chemical combinations. Western blot and enzymatic activity analysis revealed quantitative but not qualitative differences in the CYP subfamilies present in the different microsomal fractions; all of the chemicals used increased the levels of CYP1A1/2, CYP2B1/2 and CYP2E1 wi th respect to control microsomes. CYP3A was not modified by the different t reatments. When tested in the Ames test, Aroclor S9 and PB/NF S9 were the m ost effective in the activation of benzo[a]pyrene and 3-methylcholanthrene which are metabolized mainly by CYP1A1; additionally, the highest mutagenic potency of 2-aminofluorene and N-nitrosodipropylamine, which are activated by CYP1A2 and CYP2B, respectively, were obtained with PB/NF S9. All these compounds were also activated when CH/ABZ S9 was used as the exogenous sour ce of metabolism. Mutagens like N-nitrosopyrrolidine and N-nitrosodimethyla mine, activated by CYP2E1, were detected only when CH/ABZ S9 was used, and the effectiveness of the different S9 fractions in activating cyclophospham ide decreased in the following order: Aroclor = PB/NF > CH/ABZ > control. F rom these experiments we can conclude that the individual CYP- inducing pro perties of ABZ and CH complement each other when the two compounds are admi nistered in conjunction and that the resulting S9 fraction is able to activ ate several known mutagens in the Ames test.