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Aflatoxin B1 metabolism by 3-methylcholanthrene-induced hamster hepatic cytochrome P-450s

✍ Scribed by Lai, T. S. ;Chiang, J. Y. L.

Publisher: John Wiley and Sons
Year: 1990
Tongue: English
Weight: 688 KB
Volume: 5
Category: Article
ISSN: 0887-2082
DOI: 10.1002/jbt.2570050303

No coin nor oath required. For personal study only.

✦ Synopsis

We have studied the activation of aflatoxin B, by hamster liver microsomes and purified hamster cytochrome P-450 isozymes using a umu mutagen test. The hamster liver microsomes or S-9 fractions were much more active than rat liver microsomes or s-9 fractions in the activation of umu gene expression by aflatoxin B, metabolites. 3-Methylcholanthrene treatment increased aflatoxin B, activation by hamster liver microsomes. Two major 3methylcholanthrene-inducible cytochrome P-450 isozymes, P-450 MC1 (IIA) and P-450 MC4 (IA2), were purified from 3-methylcholanthrene-treated hamster liver microsomes, and the metabolism of aflatoxin B, by these two cytochromes was studied.

In the reconstituted enzyme system, both P-450 MCl and P-450 MC4 were highly active in the activation of aflatoxin B,, and antibodies against these P-450s specifically inhibited these activities. Antibody against P-450 MC1 inhibited the activation of aflatoxin B, by 20% in the presence of 3-methylcholanthrene-treated hamster liver microsomes. In contrast, antibody against P-450 MC4 stimulated the activity by 175%. These results indicated that hamster P-450 MC1 might convert aflatoxin 8, to more toxic metabolite@), whereas P-450 MC4 might convert aflatoxin B, to less toxic metabolite(s), than aflatoxin B, in liver microsomes. The metabolite(s) produced by both hamster cytochrome P-450 MC1 and MC4 were genotoxic in the umu mutagen test.

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