Effect of dipyridoimidazole pretreatment on mutagen activation in rats.

Rats were pretreated with a single oral dose of different mutagenic fractions obtained from glutamic acid pyrolysate: Glu-P-2 (2-amino-dipyrido[1,2-a:3',2'-d]imidazole), Glu-P-3 (3-amino-4,6-dimethyldipyrido[1,2-a:3',2'-d]imidazole), the tar residue and a basic extract (B2). The liver S9 fractions of these animals were used to investigate the mutagenic activation of 3 promutagens (2-aminoanthracene, Glu-P-2 and Glu-P-3) in Salmonella typhimurium strain TA1538. Different factors were analyzed; influence of the structure of the compounds administered, doses, time interval between pretreatment and sacrifice and sex of the rats.

Mutation spectrum of the mutagen 3-N,N-acetoxyacetylamino-4,6-dimethyldipyrido[1,2-a:3',2'- d]imidazole in Escherichia coli.

The mutation frequency and mutation spectrum resulting from 3-N-acetylamino-4,6-dimethyldipyrido[1,2-a:3',2'-d]imidazole (AGluP3) DNA adducts using a previously developed forward mutation assay were established. AGluP3-induced mutagenesis requires the umuC gene product(s) and exhibits similar amounts of base pair substitution and frameshift mutation. Comparison between these results and those obtained with the isosteric amine 2-N-acetylaminofluorene suggests the involvement of deacetylated adduct in the molecular mechanisms of AGluP3-induced mutagenesis.

Comparison of the reactivity of B-DNA and Z-DNA with two isosteric chemical carcinogens: 2-N,N-acetoxyacetylaminofluorene and 3-N,N-acetoxyacetylamino-4,6-dimethyldipyrido-[1,2-a:3',2' -d] imidazole.

The reactivity of nucleic acids in various conformations and two isosteric chemical carcinogens 2-N,N-acetoxyacetylaminofluorene (N-AcO-AAF) and 3-N,N-acetoxyacetylamino-4,6-dimethyldipyrido [1,2-a:3',2'-d] imidazole (N-AcO-AGlu-P-3) have been studied. Both carcinogens bind covalently to poly(dG-dC).poly(dG-dC) (B form) and to poly(dG-br5C).

In vitro enzymatic methylation of DNA modified with the mutagenic amine: 3-N,N-acetoxyacetylamino-4,6-dimethyldipyrido(1,2-a:3'2'-d )imidazole.

Both the initial velocity and the overall methylation of DNA modified by acetylamino-4,6-dimethyldipyrido(1,2-a:3',2'-d)imidazole (A-Glu-P-3) by rat liver DNA-(cytosine-5-)-methyltransferase are decreased as compared to native DNA. A-Glu-P-3 bound to guanine residues may block the movement of the enzyme along the helix. The modified DNA does not inhibit the enzymatic methylation of native DNA.

Immunological titration of 3-N-acetyl-hydroxyamino-4,6-dimethyldipyrido(1,2-a:3',2'-d) imidazole-rat liver DNA adducts.

Antibodies to N-(guanosin-8-yl)-3-N-acetylamino-4,6-dimethyldipyrido(1,2-a :3',2'-d)imidazole were elicited in rabbits by immunization with a conjugate formed between this compound and bovine serum albumin. The specificity of the antibodies was studied by radioimmunoassay. These antibodies were used to titrate the adducts formed in liver DNA of rats treated with 3-N-acetyl-hydroxyamino-4,6-dimethyldipyrido(1,2-a:3',2'-d)imidazo le,p6 a supposed metabolite of the mutagenic amine 3-amino-4,6-dimethyldipyrido(1,2-a:3',2'-d)imidazole (Glu-P-3).

Mutagenicity of some derivatives of dipyrido[1,2-a:3',2'-d]imidazoles in Salmonella typhimurium with metabolic activation by rat liver and small intestine subcellular fractions.

The mutagenic effect of 2-amino-dipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2) was compared with that of the 3-amino, 3-nitro, or 3-N-hydroxylated derivatives of the same base ring with methyl groups at positions 4 and 6 of the molecule. The compounds were tested in Salmonella typhimurium strain TA98 without metabolic activation and in the presence of different concentrations of subcellular fractions from livers or small intestines of rats pretreated with different P448/P450 inducers. The 4,6-dimethyl compounds are always more mutagenic than Glu-P-2.

Reaction of DNA with a mutagenic 3-N,N-acetoxyacetylamino-4,6-dimethyldipyrido[1,2-a:3',2'- d]imidazole (N-AcO-AGlu-P-3) related to glutamic acid pyrolysates.

3-Amino-4,6-dimethyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-3), an analog amine of the potent genotoxic Glu-P-1 isolated from a glutamic acid pyrolysate, has been chemically synthesized. Glu-P-3 was found much more mutagenic than Glu-P-1 to S. typhimurium TA 98 and TA 100 with S-9 mix.

Conformational changes induced in DNA by the in vitro reaction with the mutagenic amine: 3-N,N-acetoxyacetylamino-4,6-dimethyldipyrido (1,2-a: 3', 2'-d) imidazole.

The conformation of synthetic or natural DNAs modified in vitro by covalent binding of N-AcO-A-Glu-P-3 was investigated by fluorescence and circular dichroism. In all cases, substitution occurs mainly on the C8 of guanine residues. In modified poly(dG-dC).

C-alkylation of N-acetoxy-N-2-acetylaminofluorene: effects on its reaction with DNA in vitro.

In vitro reactions of DNA with N-acetoxy-N-2-acetylaminofluorene (N-AcO-AAF), N-acetoxy-7-ethyl-N-2-acetylaminofluorene (N-AcO-EtAAF), N-acetoxy-7-n-butyl-N-2-acetylaminofluorene (N-AcO-But-AAF) are compared. C-alkylation of N-AcO-AAF affects the reactivity of the metabolite towards DNA. The electronic effect and the size of alkyl group seem to determine the reactivity of the metabolite.

Mutagenicity of several derivatives of dipyrido[1,2-a:2',3'-d]imidazoles.

Different derivatives of dipyrido[1,2-a:2',3'-d]imidazoles have been investigated, as mutagens for Salmonella typhimurium. The nature of different substitution groups and their positions on the base ring influenced markedly the mutagenicity of these compounds. From this structure/effect relationship study, it was demonstrated that the 2 and 3 positions were of special interest.

Biochemical effects of some derivatives of dipyrido[1,2-a:3,'2'-d]imidazole related to protein pyrolysates on rat liver microsomes.

Several derivatives of dipyrido[1,2-a:3',2'-d]imidazole related to protein pyrolysates have been studied for their effects on the P-450 system of hepatic parenchyma and two dependent monoxidase enzymes, zoxazolamine hydroxylase and dimethylnitrosamine-N-demethylase (DMN-d-ase). We found that the compounds can be divided into two groups. The first group consists of compounds which inhibit the production of cytochrome P-450 and zoxazolamine hydroxylase and induce the formation of DMN-d-ase; these compounds are known to be powerful mutagens.

Spectroscopic study of the effects of C-alkylation of N-acetoxy-N-acetyl-2-aminofluorene on some properties of the carcinogen-modified DNA.

Several physicochemical properties of DNA reacted in vitro with the carcinogen metabolite N-acetoxy-N-2-acetylaminofluorene (N-AcO-AAF) are compared to those of DNA reacted with two C-alkylated derivatives, viz. N-acetoxy-7-ethyl-N-2-acetylaminofluorene (N-AcO-EtAAF) and N-acetoxy-7-n-butyl-N-2-acetylamino-fluorene (N-AcO-ButAAF). Ultraviolet absorption, high resolution derivative melting curves and circular dichroism techniques are employed in the present study.

Reactivity of B and Z-DNA towards N-acetoxy-2-acetylaminofluorene.

Poly d(G-C) d(G-C) in B-form, on one hand, and poly d(G-br5C). poly d(G-br5C) and poly d(G-m5C) . poly d(G-m5C) in Z-form, on another hand, were treated with N-AcO-[3H]AAF and the kinetics of these reactions were followed by radioactivity.

In vitro reaction of the carcinogenic derivative N-acetoxy-7-ethyl-N-2-acetylaminofluorene with DNA. A spectroscopic study.

In vitro reaction of DNA with N-acetoxy-7-ethyl-N-acetylaminofluorene (N-AcO-EtAAF is compared to that with N-acetoxy-N-acetyl-2-aminofluorene. Introduction of an ethyl group at the position 7 of the fluorene ring is found to induce an increase of reactivity of this (model) metabolite of carcinogen N-acetoxy-2-aminofluorene (2-AAF) toward DNA and its constituents. Spectroscopic methods (u.

Antibodies to N-hydroxy-2-aminofluorene modified DNA as probes in the study of DNA reacted with derivatives of 2-acetylaminofluorene.

Antibodies were elicited in rabbits immunized with a mixture of methylated bovine serum albumin and N-hydroxy-2-aminofluorene reacted DNA (DNA-AF). These antibodies were used in competition radioimmunoassays (RIA) with [3H]DNA-AF as radioactive antigen and different N-acetoxy-2-acetylaminofluorene (N-AcO-AAF) and N-hydroxy-2aminofluorene (N-OH-AF) reacted DNAs, deoxyguanosine, dGMP, dGpA and dApG as inhibitors. Based on the results of RIA it is concluded that the binding sites of the two residues, -AF and -AAF, to guanosine in DNA, are essentially the same.

Genetic effects of chlorinated anilines and azobenzenes on Salmonella typhimurium.

The mutagenicity of 19 herbicide-derived chlorinated azobenzenes and structurally related chlorinated anilines and nitrobenzenes was assayed towards several strains of S. typhimurium, using the plate incorporation method and the fluctuation test, in the presence or in the absence of liver post-mitochondrial fractions, in aerobic and anerobic conditions. Positive results were obtained with 4,4'-dichloroazobenzene, 4,4'-dichloroazoxybene, 3,4-dichloronitrobenzene and, to a much lesser extent, with 3,4,3',4'-tetrachloroazobenzene.

Alkaline stability of guanosine and some of its derivatives modified by the carcinogen N-acetoxyacetylaminofluorene.

The alkaline treatment of Guo, dGuo, dGMP and denatured DNA modified by N-acetoxyacetylaminofluorene (N-AcO-AAF) was performed in 0.1 M NaOH at 40 degrees C. The kinetics of the reaction were followed by ultraviolet absorption and by chromatographic methods and were found different for the four products under study.

Conformational changes induced in DNA by in vitro reaction with N-hydroxy-N-2-aminofluorene.

The conformation of DNA modified in vitro by the covalent binding of N-OH-AF was investigated by ultraviolet absorbance, circular dichroism and by radioimmunoassay using specific antibodies against Guo-AAF and nDNA-AAF. The results obtained by both physico-chemical and immunological methods are in agreement with a model involving destabilized regions in the double helical DNA around the carcinogen molecule in which, however, the -AF residues are stacked to the adjacent nucleotides. The RIA results show that the -AF residues are less accessible to antibodies in native than in denatured DNA-AF and thus suggest -AF residues partially buried in the interior of the DNA helix.

[Similarities in the biochemical effects of tetrachloro 2,3,7,8 dibenzo-p-dioxin and tetrabromo-2,3,7,8 dibenzo-p-dioxin on rats].

Screening tests for the study of carcinogenic compounds showed that 2,3,7,8-tetrabromodibenzo-p-dioxin was at least as active as 2,3,7,8-tetrachlorodibenzo-p-dioxin in regard to its effect on the in vivo synthesis of zoxanzolamine hydroxylase and on the arginase activity of the liver. The biological properties of these compounds seem to be due to the symmetry of their m molecular structure.

Biochemical effects of 2-aryl- and 2,3-diarylindoles on the biosynthesis of zoxazolamine hydroxylase in rats.

In continuation of our pharmacological research on the in vivo induction or inhibition of the drug metabolizing enzymes system, a series of 32 derivatives of indole bearing aryl substituents in position 2 and 3 were investigated in regard to their effect on the in vivo synthesis of zoxazolamine hydroxylase in the young rat. Most fo the compounds examined proved to be inducers of this enzyme; however, as is the case with polycyclic carcinogens, the inducing activity was found to be significantly dependent on molecular structure.