Mutagenic activation of 2,4-diaminoanisole and 2-amino-fluorene by isolated rat liver nuclei and microsomes

Final Report on the Safety Assessment of 4-Methoxy-m-Phenylenediamine, 4-Methoxy-m-Phenylenediamine Sulfate, and 4-Methoxy-m-Phenylenediamine-HCl

The hair dye ingredient 4-Methoxy-m-Phenylenediamine Sulfate (4-MMPDS) prior to 1978 was used extensively used in the United States. Concerns raised because of studies which showed the hair dye to be an animal carcinogen prompted the voluntary reformulation and deletion of 4-MMPD in hair dyes containing this ingredient. No reports were made on the use of this ingredient until 1989 when 17 uses were reported. Assays on volunteers indicate that less than 0.2% of the dye penetrates the scalp and that about 3.9% is absorbed through the skin of the forearm. The dye is metabolized and excreted in the urine; a major metabolic product was 4-acetylamino-2-aminoanisole. The LD50 range in rats of aqueous solutions of 4-MMPD was 400–500 mg/kg. No gross tissue abnormalities were reported in subchronic feeding or dermal studies. 4-MMPD was not an ocular irritant when tested at 2.5%, but was a mild skin irritant when tested at the same concentration. The dermal application of hair dye formulations containing up to 4.0% 4-MMPD were negative for both embryotonic toxicity and teratogenic effects. The results of numerous mutagenic studies vary between the assay system used. 4-MMPD was noncarcinogenic in four dermal carcinogenic studies, but was carcinogenic to both rats and mice in feeding studies. On the basis of the information included in this report, it is concluded that 4-Methoxy-m-Phenylenediamine, 4-Methoxy-m-Phenylenediamine Sulfate, and 4-Methoxy-m-Phenylenediamine HCl are unsafe for use in cosmetic products.

Effect of dietary trans fatty acids on microsomal enzymes and membranes

Three groups of rats were maintained on diets containing different proportions of trans fatty acids (0, 18.3 or 36.6% of the total fatty acids) for eight weeks. No differences in body weight were observed among the three groups, but the fat cell size, determined in epididymal fat, differed significantly between the controls and the rats fed diets containing trans fatty acids. The supernatant obtained by centrifuging homogenates of liver from the rats at 9000 X g (S-9 fraction) was used as an activator in a bacterial test for mutagenicity of 2-aminofluorene and aflatoxin B1 using Salmonella typhimurium strains TA 98 and TA 100, respectively. The mutagenicities of 2-aminofluorene in strain TA 98 and of aflatoxin B1 in strain TA 100 were significantly lower with the liver S-9 fraction from rats fed a diet containing 36.6% trans fatty acids than with the liver S-9 fraction from rats fed a control diet with no trans fatty acids.

Mutagenic relevance of rat hepatocyte nuclei in the activation and inactivation of xenobiotica. Cyclophosphamide and epichlorohydrin activity on the yeasts S. pombe and S. cerevisiae

The influence on the mutagenicity of cyclophosphamide (Cy) and epichlorohydrin (ECH), of liver nuclei and hepatic post-mitochondrial (S9) preparations from phenobarbital-treated rats, was examined. The study was conducted in vitro, with 2 yeasts, Schizosaccharomyces pombe (P1 strain) which allows the detection of forward mutations, and Saccharomyces cerevisiae (D5 strain), in which the induction of different genetic effects, such as mitotic recombination, can be evaluated. The results indicated that the nuclear fraction has a qualitative capacity for biotransformation of compounds, overlapping that of S9. From a quantitative point of view, the Cy-activating capacity of the nuclear fraction was twice as high as that of S9 whereas the two fractions showed a similar ECH-inactivating ability. The present study strengthens the hypothesis of the relevance of nuclei as a site of metabolic activation and inactivation of exogenous compounds.

Influence of conjugation reactions on the mutagenicity of aromatic amines

2-Acetylaminofluorene (AAF) and 2-aminofluorene (AF), as well as their N-hydroxylated metabolites, N-OH-AAF and N-OH-AF, were studied for mutagenic effects in Salmonella typhimurium with rat- and mouse-liver S9 and microsomal subfractions in the presence of cofactors for glucuronidation and glutathione (GSH) transfer. Addition of UDPGA did not affect the mutagenicity of AAF, AF or N-OH-AAF under any experimental condition. Addition of GSH, on the other hand, markedly inhibited AAF, AF and N-OH-AAF. This seemed to be due to the direct effect of GSH, and not through an enzyme-catalyzed conjugation. Further, GSH inhibited the direct mutagenicity of N-OH-AF.