TY - JOUR
T1 - The Role of Acetylation in Benzidine Metabolism and DNA Adduct Formation in Dog and Rat Liver
AU - Lakshmi, Vijaya M.
AU - Zenser, Terry V.
AU - Goldman, H. Duane
AU - Davis, Bernard B.
AU - Gupta, Ramesh C.
AU - Spencer, Glenda G.
AU - Hsu, Fong Fu
PY - 1995/7
Y1 - 1995/7
N2 - To determine whether benzidine is acetylated in dog, like rat, the metabolism of benzidine was assessed with dog and rat liver slices. Slices were incubated with 0.05 mM [3H]benzidine for 4 h. Media and cellular DNA were analyzed for acetylated benzidine metabolites and adducts. In rat, benzidine was rapidly converted to acetylated metabolites. At 1 h, benzidine, N-acetylbenzidine, and N,N'-diacetylbenzidine represented 5%, 23%, and 54%, respectively, of the total radioactivity in media. Within 2 h, 75% of the radioactivity was N,N' diacetylbenzidine. In dog, 45% of the radioactivity was present in metabolites more polar than benzidine by 4 h. No N-acetylated metabolites were observed in dog liver slice media. To identify acetylated benzidine DNA adducts, N-(deoxyguanosin-8-yl)-N,N'-diacetylbenzidine was prepared and identified by FAB MS. This nucleoside adduct was used to synthesize N-(deoxyguanosin-8-yl)-N-acetylbenzidine and N'-(deoxyguanosin-8-yl)-N-acetylbenzidine. Nucleoside adducts from slices incubated with [3H]benzidine were analyzed by HPLC. With this method of analysis, the 3H-material did not correlate with the synthetic adduct standards. To improve sensitivity and identify liver adducts, a 32P-postlabeling method was developed. 2'-Deoxyguanosine 3'-monophosphate adduct standards of acetylated benzidine were prepared. 32P-Postlabeling analysis demonstrated that rat liver contained only (N'-(3'-monophosphodeoxyguanosine-8-yl)-N-acetylbenzidine after a 1- or 4-h exposure to benzidine. In contrast, no acetylated adducts were detected in dog. Results indicate that dog is a nonacetylator with respect to benzidine. The availability of acetylated benzidine nucleotide standards allowed unambiguous identification of N'-(3'-monophosphodeoxyguanosin-8-yl)-N-acetylbenzidine as the adduct present in rat liver slices. These nucleotide adduct standards will be useful in subsequent studies in animals and human.
AB - To determine whether benzidine is acetylated in dog, like rat, the metabolism of benzidine was assessed with dog and rat liver slices. Slices were incubated with 0.05 mM [3H]benzidine for 4 h. Media and cellular DNA were analyzed for acetylated benzidine metabolites and adducts. In rat, benzidine was rapidly converted to acetylated metabolites. At 1 h, benzidine, N-acetylbenzidine, and N,N'-diacetylbenzidine represented 5%, 23%, and 54%, respectively, of the total radioactivity in media. Within 2 h, 75% of the radioactivity was N,N' diacetylbenzidine. In dog, 45% of the radioactivity was present in metabolites more polar than benzidine by 4 h. No N-acetylated metabolites were observed in dog liver slice media. To identify acetylated benzidine DNA adducts, N-(deoxyguanosin-8-yl)-N,N'-diacetylbenzidine was prepared and identified by FAB MS. This nucleoside adduct was used to synthesize N-(deoxyguanosin-8-yl)-N-acetylbenzidine and N'-(deoxyguanosin-8-yl)-N-acetylbenzidine. Nucleoside adducts from slices incubated with [3H]benzidine were analyzed by HPLC. With this method of analysis, the 3H-material did not correlate with the synthetic adduct standards. To improve sensitivity and identify liver adducts, a 32P-postlabeling method was developed. 2'-Deoxyguanosine 3'-monophosphate adduct standards of acetylated benzidine were prepared. 32P-Postlabeling analysis demonstrated that rat liver contained only (N'-(3'-monophosphodeoxyguanosine-8-yl)-N-acetylbenzidine after a 1- or 4-h exposure to benzidine. In contrast, no acetylated adducts were detected in dog. Results indicate that dog is a nonacetylator with respect to benzidine. The availability of acetylated benzidine nucleotide standards allowed unambiguous identification of N'-(3'-monophosphodeoxyguanosin-8-yl)-N-acetylbenzidine as the adduct present in rat liver slices. These nucleotide adduct standards will be useful in subsequent studies in animals and human.
UR - http://www.scopus.com/inward/record.url?scp=0029005021&partnerID=8YFLogxK
U2 - 10.1021/tx00047a011
DO - 10.1021/tx00047a011
M3 - Article
C2 - 7548754
AN - SCOPUS:0029005021
SN - 0893-228X
VL - 8
SP - 711
EP - 720
JO - Chemical Research in Toxicology
JF - Chemical Research in Toxicology
IS - 5
ER -