Aryl-monoalkyl and cyclic triazenes: direct-acting mutagens

Molecular models that may account for nitrous acid mutagenesis in organisms containing double-stranded DNA

Nitrous acid (NA) is often presumed to cause base substitutions in organisms with double-stranded DNA as a direct consequence of oxidative deamination of adenine and of cytosine residues. Here we summarize evidence indicating that other mechanisms are involved in the case of NA-induced G/C-->A/T transition mutations. We present several models for pathways of NA mutagenesis that may account for our experimental results and overlapping data noted in the literature. One model proposes that the base substitution mutations observed are due to DNA alkylation damage mediated via nitrosation of polyamines and/or other ubiquitous cellular molecules. Other models assume that predisposing lesions, such as G-to-G cross-links, are first formed. The cross-links are pictured as leading to perturbations in DNA structure that allow subsequent opportunity for NA-induced deaminations of cytosine residues in their immediate vicinity. The deaminations preferentially result in G/C-->A/T transition mutations at sites highly dependent on adjoining base sequence context (i.e., in NA "mutational hotspots"). A final model proposes that NA-induced G/C-->A/T transition mutations arise mainly from oxidative deamination of guanosine residues and not from deamination of cytosine residues in duplex DNA.

Induction of chromosomal aberrations and 8-azaguanine-resistant mutations by aryldialkyltriazenes in cultured mammalian cells

Inducibility of chromosomal aberrations, cell survival, and mutation to 8-azaguanine (8AG) resistance in cultured V79 cells by 1-phenyl-3,3-dimethyltriazene (PDMT), 1-phenyl-3,3-diethyltriazene (PDET), and 1-(pyridyl-3)-3,3-diethyltriazene (PyDET) were examined with or without metabolic activation. Chromosomal aberrations were induced in a dose-dependent manner by all 3 triazenes in a direct treatment for 24 h. Chromosomal aberrations were also induced by PDMT with metabolic activation system for 3 h, and little differences in the incidences were observed compared with those obtained by a direct treatment. All 3 triazenes were slightly mutagenic in a direct treatment for 24 h. In metabolic activation experiments, however, PDMT and PyDET were highly mutagenic. The mutagenicity, when compared with the cytotoxicity, was significantly higher in a metabolic activation system than in a direct treatment.

Mutagenicity of trialkyltriazenes: mutagenic potency of alkyldiazonium ions, the putative ultimate carcinogens from dialkylnitrosamines

Although aryldialkyltriazenes have been known for many years and their mutagenic, carcinogenic and carcinostatic properties have been investigated, almost nothing is known of the related trialkyltriazenes. Our recently developed general preparative route to these substances has allowed the examination of the mutagenic properties of several representative examples of this class of compounds. This, 1-benzyl-3,3-dimethyl-, 3-benzyl-1,3-dimethyl, 3-benzyl-3-methyl-1-n-butyl- and 1,3-di-n-butyl-3-methyltriazenes are direct acting mutagens in the TA1535 strain of Salmonella typhimurium. The respective mutagenic potencies of these substances can be accounted for by the in situ generation of alkyldiazonium ions. These ions are considered to be strong candidates for the ultimate mutagens/carcinogens derived from some dialkylnitrosamines.

Potential carcinogenic and mutagenic industrial chemicals. I. Alkylating agents

A variety of alkylating agents, acylating agents, peroxides, halogenated derivatives, and nitrogen derivatives have been reviewed, principally in terms of their synthesis, areas of utility, stability, distribution, reactivity, levels of exposure, population at risk, metabolism, carcinogenicity, and mutagenicity.