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  • Title: 2-Methoxy-4-nitroaniline and its isomers induce cytochrome P4501A (CYP1A) enzymes with different selectivities in the rat liver.
    Author: Degawa M, Nakayama M, Konno Y, Masubuchi K, Yamazoe Y.
    Journal: Biochim Biophys Acta; 1998 Mar 02; 1379(3):391-8. PubMed ID: 9545601.
    Abstract:
    We reported previously that 2-methoxy-4-nitroaniline (2-MeO-4-NA) is a selective inducer of cytochrome P4501A2 (CYP1A2) in the rat liver, and its molecular size is the smallest among known CYP1A2-selective inducers. In the present study, a structure-activity relationship on the CYP1A2-selective induction has been investigated using isomeric nitroanisidines and their related chemicals. Western blot analyses revealed that the chemicals removed a substituent (amino, methoxyl or nitro group) from a 2-MeO-4-NA molecule had no capacity for inducing CYP1A enzymes in rat livers. On the other hand, isomeric nitroanisidines such as 2-MeO-4-NA, 2-MeO-5-NA and 4-MeO-2-NA induced both CYP1A2 and CYP1A1 enzymes with different selectivities. As judged from the induced levels of CYP1A proteins, 2-MeO-4-NA (CYP1A2/CYP1A1 ratio; 9.5) and 4-MeO-2-NA (0.3) were the most selective inducers of CYP1A2 and CYP1A1, respectively, among the isomeric nitroanisidines (0.44 mmol/kg) used. The induced level of CYP1A2 protein was in the order 2-MeO-4-NA > 2-MeO-5-NA > 4-MeO-2-NA, although no significant difference was observed on their CYP1A2 mRNA level. On the contrary, increases in the levels of CYP1A1 mRNA and protein were in the order 4-MeO-2-NA > 2-MeO-5-NA > 2-MeO-4-NA. The present findings indicate that all three substituents (amino, methoxyl and nitro groups) are necessary components of nitroanisidines for induction of CYP1A enzymes, and also show that regio-isomeric positions of these substituents determine the selectivity in the induction of CYP1A enzymes.
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