This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Morton, K. C. Articles by Baetcke, K. P. Search for Related Content PubMed PubMed Citation Articles by Morton, K. C. Articles by Baetcke, K. P.

Metabolism of Benzidine to N-Hydroxy-N,N'-diacetylbenzidine and Subsequent Nucleic Acid Binding and Mutagenicity¹

Division of Molecular Biology, National Center for Toxicological Research, United States Department of Health, Education, and Welfare, Jefferson, Arkansas 72079

Evidence has been obtained that benzidine metabolism can include the following sequence: benzidine N-acetylbenzidine N,N'-diacetylbenzidine N-hydroxy-N,N'-diacetylbenzidine nucleic acid binding. Benzidine was acetylated in a two-step, acetyl-CoA-dependent reaction catalyzed by liver cytosol from hamsters, guinea pigs, mice, and rats (listed in order of decreasing enzyme activity); the products N-acetylbenzidine and N,N'-diacetylbenzidine were identified by thinlayer and high-pressure liquid chromatography and by mass spectrometry. The first acetylation step was more rapid than was the second in all species except the guinea pig, where the rates were equal. N,N'-Diacetyl[ring-U-¹⁴C]benzidine was hydroxylated by fortified liver microsomes (hamster > mouse > rat) to yield both N-hydroxy- and 3-hydroxy-N,N'-diacetyl[ring-U-¹⁴C]benzidine, which were identified by isotopic dilution and/or mass spectrometry. Isotopic dilution experiments did not detect the formation of N-acetyl-N'-glycolyl-[ring-U-¹⁴C]benzidine during these incubations. Pretreatment of animals with 3-methylcholanthrene enhanced N- and 3-hydroxylation in all cases except for 3-hydroxylation by hamsters. Chemically synthesized N-hydroxy-N-acetyl-N'-[1-¹⁴C]acetylbenzidine bound to transfer RNA in the presence of liver cytosol. The binding was catalyzed by an N,O-acyltransferase which varied in the order hamster > rat > mouse. N-Hydroxy-N,N'-diacetylbenzidine was mutagenic for Salmonella typhimurium TA 1538 in the presence of a partially purified N,O-acyltransferase preparation. These data suggest that BZ can be metabolized to reactive derivatives which may contribute to the induction of tumors.

¹ Preliminary reports of this study were presented previously (40, 41).

² Supported by Interagency Agreement 224-75-0002 between the Veterans Administration Hospital, Little Rock, Ark. 72206 and the Food and Drug Administration, United States Department of Health, Education, and Welfare, Jefferson, Ark. 72079. To whom requests for reprints should be addressed. Present address: Michigan Cancer Foundation, 110 East Warren Avenue, Detroit, Mich. 48201.

³ Appointee of the National Cancer Institute. Present address: Michigan Cancer Foundation, 110 East Warren Avenue, Detroit, Mich. 48201.

Received 7/24/78. Accepted 5/ 8/79.

This article has been cited by other articles:

				V. M. Lakshmi, T. V. Zenser, and B. B. Davis Rat Liver Cytochrome P450 Metabolism of N-Acetylbenzidine and N,N'-Diacetylbenzidine Drug Metab. Dispos., April 1, 1997; 25(4): 481 - 488. [Abstract] [Full Text]