Preferential activation of 6-aminochrysene and 2-aminoanthracene to mutagenic moieties by different forms of cytochrome P450 in hepatic 9000 X g supernatants from the rat.
6-Aminochrysene and 2-aminoanthracene were activated to metabolites which were mutagenic to Salmonella typhimurium TA98 by hepatocytes or hepatic 9000 X g supernatants (S9s) from control or xenobiotic-treated rats. Hepatocytes from Aroclor-1254-treated rats were more efficient than hepatocytes from untreated rats at activating these aromatic amines. When plate-incorporation and liquid-incubation bacterial mutagenesis assays were performed in the presence of limiting amounts of rat hepatic S9, 2-aminoanthracene was activated to a greater extent in both cases, as judged by his+ revertant formation, by 3-methylcholanthrene-induced hepatic S9 than by phenobarbital-induced or control S9s. In contrast, 6-aminochrysene was activated more efficiently by phenobarbital-induced S9 than by 3-methylcholanthrene-induced or control S9s. This unexpected finding was confirmed employing polyclonal antibodies directed against specific forms of rat cytochrome P450. Thus, when employing Aroclor-1254-induced S9 as a source of metabolic activation, antibody directed against cytochrome P450IA1 inhibited the activation of 2-aminoanthracene but not of 6-aminochrysene. In contrast, antibody directed against cytochrome P450IIB1 inhibited the activation of 6-aminochrysene but not of 2-aminoanthracene. These results suggest that under conditions in which the amounts of S9 added are rate-limiting, the two aromatic amines are preferentially activated by different induced forms of cytochrome P-450.
Lubet
R A
RA
Department of Genetic Toxicology, Microbiological Associates, Bethesda, MD 20816.
McKinney
C E
CE
Cameron
J W
JW
Guengerich
F P
FP
Nims
R W
RW
D000818:Animals; D000873:Anthracenes / Q000378:metabolism*; D001711:Biotransformation; D002911:Chrysenes / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism*; D009152:Mutagenicity Tests; D009153:Mutagens / Q000378:metabolism; D010616:Phenanthrenes / Q000378:metabolism*; D051381:Rats; D012486:Salmonella typhimurium / Q000187:drug effects; D013347:Subcellular Fractions
D000873:Anthracenes; D002911:Chrysenes; D009153:Mutagens; D010616:Phenanthrenes; C006593:2-anthramine; D003577:Cytochrome P-450 Enzyme System; C100101:6-chrysenamine