In vitro and in vivo benzo(a)pyrene metabolism in rat liver and lung microsomes: effect of sodium selenite.

In vitro, the addition of various concentrations of sodium selenite (Na2SeO3, 5H2O) to liver and lung microsomal fractions of rats previously treated with 3-methylcholanthrene shows a decrease in the different benzo(a)pyrene (B(a)P) metabolites. This inhibition varies, depending on the metabolite considered and in relation to both the selenium level and the origin of the microsomal suspension. In vivo, on rats treated with B(a)P or B(a)P+ Na2SeO3, the results show a high aryl hydrocarbon hydroxylase (A.H.H) activity in lung microsomes; however selenium does not exhibit any effect. The slight increase of lung cytochrome P450 levels is not significant. Moreover, B(a)P and B(a)P+ Na2SeO3 do not induce any effect on liver A.H.H activity and cytochrome P450 levels. The insufficient Se concentration in the tissues could explain the lack of in vivo effect.