Mutagenicity of benzidine and related compounds employed in the detection of hemoglobin

The genetic toxicology of ortho-toluidine

ortho-Toluidine, a monosubstituted aniline and an intermediate in the dyeing industry, with a number of uses in other fields such as rubber processing and pharmaceutical production, has been in production for over 100 years. It is metabolised in vivo into a number of compounds, some of which are active genotoxins. It has been demonstrated to be a carcinogen in mice and rats and is a suspected human carcinogen. o-Toluidine has a wide range of genetic effects. It is a weak bacterial, fungal and mammalian mutagen, although the conditions required are stringent. The metabolising system used is of particular importance. o-Toluidine is also a clastogen, generally on prolonged exposure. It induces aneuploidy in both fungi and mammalian cultured cells. It also produces DNA damage (single-strand breaks and unscheduled DNA synthesis, UDS) and causes cell transformation. o-Toluidine can be considered a general genotoxin demonstrable under special conditions, particularly with regard to metabolism.

Structure-activity relationships of aromatic amines in the Ames Salmonella typhimurium assay

The author tried in a somewhat limited work to quantitatively correlate the electronic and steric intramolecular interactions of substituents on the amino group (influencing the enzymatic reactions of aromatic amines) and the mutagenic event. It was assumed that there is a correlation between these biotransformations and the electronic state of aromatic amines at the ionic dissociation equilibrium. The approach is rather empirical and arbitrary but the overall agreement between experimental mutagenic potencies and the values calculated was encouraging and led the author to further developments. It is hoped that the concepts used in this work may be applied to other aromatic molecules bearing an amino group.

Enzymatic assay of hemoglobin in tissue homogenates with chlorpromazine

An assay of hemoglobin in tissue homogenates is described. Tissues are homogenized with a 40 mM phosphate buffer (pH 8.0) solution without the use of a polytron or sonicator. The assay should be carried out before fractionations such as centrifugation. By measuring the free-radical intermediates of chlorpromazine, which are formed by the addition of hemoglobin, a linear calibration curve can be obtained within the range of hemoglobin contents between 0.8 and 12.0 micrograms. The present method can be applied to the assay of hemoglobin in several kinds of tissues from rats.

The Salmonella typhimurium/mammalian microsomal assay. A report of the U.S. Environmental Protection Agency Gene-Tox Program

The Salmonella assay has been in use for almost 15 years and can be defined as a routine test for mutagenicity and for predicting potential carcinogenicity. It detects the majority of animal carcinogens and consequently plays an important role in safety assessment. The test is also routinely used as the frontline screen for environmental samples (complex mixtures) isolated from air, water and food. This role will continue to remain an area of growth as or because sample volumes associated with these testing areas are generally very limited and more extensive testing is generally impossible. While this test, like all others, has some limitations, it is recommended that it be regularly included in all genetic testing batteries.

A review of the genotoxicity of food, drug and cosmetic colours and other azo, triphenylmethane and xanthene dyes

The genetic toxicology of the major dyestuffs used in foods, drugs and cosmetics has been reviewed. Published data for azo, triphenylmethane and xanthene dyes from short-term assays for muta-carcinogenicity have been summarized and discussed according to usage, current and previous worldwide legislative status. Certain other synthetic food dyes, commercial mixtures, natural and polymeric colourants as well as a section on aminoazobenzene and its derivatives have been included. Genotoxicity has been discussed with reference to structural chemistry, levels of exposure, absorption and metabolism and to epidemiological information. The extent of agreement between data from different tests and correlations with animal cancer assays have been considered. Synthetic dyes from the 3 major structural classes exhibit genotoxicity, whilst only 2 natural colours have proved active. Activity may be due to the presence of certain functional groups, notably nitro- and amino-substituents which are metabolized to ultimate electrophiles that may be stabilized by electronic interaction with aryl rings. Metabolic processes such as azo-reduction may be activating or detoxifying. the low but significant correlation between animal carcinogenicity and short-term test data may be increased with further screening, especially involving chromosome assays. It is suggested that a human cancer hazard may exist where significant quantities of finished benzidine dye samples are handled. Such risks from exposures to other colours and the possibility of human germ-line mutation induction by dyestuffs cannot be meaningfully assessed.

Mutagenicity of constituents identified in pulp and paper mill effluents using the Salmonella/mammalian-microsome assay

About 300 compounds have been reported in the literature as constituents of pulp-mill effluent. Previously, in our screening program, 10 resin acids identified in effluent were examined for potential mutagenicity in the Salmonella/mammalian-microsome assay. Neoabietic acid was the only resin acid which was found to be mutagenic. Now, a program to screen for mutagenicity of 48 additional compounds, belonging to chemical classes of chlorinated aliphatic and aromatic hydrocarbons, phenols, aldehydes, quinones, and carboxylic acids, has been completed. Only 2 of these compounds, tetrachloropropene and pentachloropropene, were found to be mutagenic, showing dose-related increases in His+ reversion mutations, in the standard Salmonella test. Metabolic activation with a preparation of Aroclor 1254-induced liver homogenate (S9) greatly reduced the mutagenic responses of these 2 compounds. Modifications of the Salmonella test for volatile mutagens enabled the detection of the mutagenicity of 3 additional chlorinated aliphatic hydrocarbons dichloromethane, dichloroethane and trichloroethane.

On the mutagenic action of some enzyme immunoassay substrates

The mutagenic action of six compounds used in ELISA, EMIT and EIA assays, was investigated by means of the fluctuation test, with Klebsiella pneumoniae as a test organism, and the Ames' plate incorporation test using Salmonella typhimurium TA 98, TA 100 and TA 1537. It appears that 2,2'-azino-di(3-ethyl-benzthiazoline sulphonic acid (6)) or ABTS exerts mutagenic action on Klebsiella pneumoniae at a concentration of 11 g/l, on Salmonella typhimurium TA 100 at a top agar concentration of 0.1 g/l, on Salmonella typhimurium TA 98 at 0.2 g/l and on Salmonella typhimurium TA 1537 at 10 g/l. With umbelliferone, mutagenic action was found only with Klebsiella pneumoniae at a concentration of 0.8 g/l or higher. With o-phenylenediamine, strong mutagenic activity was found only with strain TA 98 and metabolic activation at a top agar concentration of 0.001 g/l. With 5-aminosalicylic acid, beta-methylumbelliferone and p-nitrophenyl-phosphate, no mutagenic action was observed.

Metabolism of o-[methyl-14C]toluidine in the F344 rat

1. Following a single dose (400 mg/kg s.c.) of o-[methyl-14C]toluidine to male F344 rats, 56% of the 14C was recovered in the 24 h urine, 2.3% in the faeces and 1% as exhaled 14CO2. After 48 h, 83.9% of the 14C appeared in the urine, 3.3% in the faeces and 1.4% was exhaled. 2. Ether-extractable urinary metabolites were separated by h.p.l.c. and identified as: o-toluidine (5.1% dose); azoxytoluene (0.2%); o-nitrosotoluene (less than or equal to 0.1%); N-acetyl-o-toluidine (0.2%); N-acetyl-o-aminobenzyl alcohol (0.3%); 4-amino-m-cresol (0.6%); N-acetyl-4-amino-m-cresol (0.3%); anthranilic acid (0.3%) and N-acetylanthranilic acid (0.3%). 3. Acid-conjugated urinary metabolites (51% of dose), separated by paper electrophoresis and by Sephadex LH-20 chromatography, were identified as sulphates of 4-amino-m-cresol (27.8% dose), N-acetyl-4-amino-m-cresol (8.5%), and 2-amino-m-cresol (2.1%), and glucuronides of 4-amino-m-cresol (2.6%), N-acetyl-4-amino-m-cresol (2.8%) and N-acetyl-o-aminobenzyl alcohol. Evidence for a double acid conjugate of 4-amino-m-cresol was also found. 4. These results show that N-acetylation and hydroxylation at the 4 position of o-toluidine are major metabolic pathways in the rat. Minor pathways include hydroxylation at the 6 position, oxidation of the methyl group and oxidation of the amino group. Sulphate conjugates predominate over glucuronides by a ratio of 6:1.