Species-specific activation of phenacetin into bacterial mutagens by hamster liver enzymes and identification of N-hydroxyphenacetin O-glucuronide as a promutagen in the urine.
Phenacetin was mutagenic in Salmonella typhimurium TA100 in plate assays when liver fractions from Aroclor-treated hamsters, but not rats, were used. Its known or putative metabolites were synthesized; of these, N-hydroxyphenacetin and N-acetoxyphenacetin were found to be mutagenic in liquid and plate assays, both requiring activation by liver fractions from Aroclor-treated hamsters. 2-Hydroxyphenacetin and 2-acetoxyphenacetin were nonmutagenic. N-Hydroxyphenetidine (the deacetylated metabolite of phenacetin) and p-nitrosophenetole were the only products that were found to be mutagenic per se when assayed under N2 in either Salmonella TA100 and TA100 NR (nitroreductase-deficient) strains. Phenacetin was administered to male BDVI rats and Syrian golden hamsters, and its urinary metabolites were deconjugated with beta-glucuronidase:arylsulfatase. After reactivation by hamsters liver fractions, mutagenicity was demonstrated in S. typhimurium TA100 with urine from phenacetin-treated hamsters, but not with that from rats. After treatment with deconjugating enzymes, N-hydroxyphenacetin was isolated from hamster urine by high-performance liquid chromatography and identified by mass spectral analysis. The data support the conclusions that (a) N-hydroxyphenacetin is a proximate mutagenic metabolite of phenacetin which, after N-deacylation, is responsible for the mutagenicity observed in vitro and in the urine of hamsters and (b) the higher yield of N-hydroxyphenacetin that is formed in the liver of hamsters as compared to rats explains the pronounced species-specific activation of phenacetin into bacterial mutagens.
D000818:Animals; D001711:Biotransformation; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008297:Male; D009152:Mutagenicity Tests; D009153:Mutagens / Q000302:isolation & purification*; D009154:Mutation; D010615:Phenacetin / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology / Q000652:urine; D051381:Rats; D011919:Rats, Inbred Strains; D012486:Salmonella typhimurium / Q000187:drug effects
D009153:Mutagens; C023493:N-hydroxyphenacetin glucuronide; D010615:Phenacetin