Genotoxicity of neurotoxic triaryl phosphates: identification of DNA adducts of the ultimate metabolites, saligenin phosphates.
2-Phenoxy-4H-1,3,2-benzodioxaphosphorin 2-oxide is an electrophilic and neurotoxic metabolite of o-tolyl phosphates. We have investigated the genotoxicity of this saligenin phosphate and the structure of adducts formed by incubation of 2-phenoxy-4H-1,3,2-benzodioxaphosphorin 2-oxide with nucleosides and DNA. o-Tolyl phosphate was mutagenic in the Ames test (695 revertants/mumol, Salmonella typhimurium TA 100) only with metabolic activation. 2-Phenoxy-4H-1,3,2-benzodioxaphosphorin 2-oxide, which is a cyclization product similar to those expected from o-tolyl phosphate, was a potent mutagen in bacteria (1452 revertants/mumol, S. typhimurium TA 100) which did not require metabolic activation. Incubation of 2-phenoxy-4H-1,3,2-benzodioxaphosphorin 2-oxide with guanosine, deoxycytidine, and deoxyadenosine resulted in formation of guanosine, deoxyuridine, and adenine adducts. These were identified as N-2-(o-hydroxybenzyl)guanosine, N-3-(o-hydroxybenzyl)deoxyuridine, N-1-(o-hydroxybenzyl)adenine, and N-3-(o-hydroxybenzyl)adenine by 1H-NMR spectroscopy, thermospray mass spectrometry, and pH-dependent electronic spectrometry. The deoxyuridine adduct is formed by an alkylation at N-3 of deoxycytidine followed by conversion of the adjacent exocyclic imino group to carbonyl (hydrolytic deamination). The formation of N-2-(o-hydroxybenzyl)-deoxyguanosine, N-3-(o-hydroxybenzyl)deoxyuridine, and N-1-(o-hydroxybenzyl)deoxyadenosine was also demonstrated when 2-phenoxy-4H-1,3,2-benzodioxaphosphorin 2-oxide was incubated with calf thymus DNA. Adducts formed with nucleosides in calf thymus DNA reacted with 2-phenoxy-4H-1,3,2-benzodioxaphosphorin 2-oxide in vitro were detected by the 32P-postlabeling technique and identified by comparison with synthetic references. DNA adducts are formed by an o-hydroxybenzylation from cyclic phosphoranes derived from o-alkyl-substituted triaryl phosphates.(ABSTRACT TRUNCATED AT 250 WORDS)
Mentzschel
A
A
Institut für Toxikologie, Universität Würzburg, Federal Republic of Germany.
Schmuck
G
G
Dekant
W
W
Henschler
D
D
D000818:Animals; D001592:Benzyl Alcohols / Q000378:metabolism / Q000633:toxicity*; D004247:DNA / Q000032:analysis* / Q000187:drug effects; D009152:Mutagenicity Tests; D009153:Mutagens / Q000378:metabolism / Q000633:toxicity*; D009422:Nervous System Diseases / Q000139:chemically induced*; D051381:Rats; D012486:Salmonella typhimurium / Q000235:genetics; D014317:Tritolyl Phosphates / Q000378:metabolism / Q000633:toxicity*
D001592:Benzyl Alcohols; D009153:Mutagens; D014317:Tritolyl Phosphates; D004247:DNA; C010631:salicyl alcohol