3-Chloro-p-toluidine hydrochloride: in vitro mutagenicity studies for human health hazards determinations.

3-Chloro-p-toluidine hydrochloride (CPT-HCl) is an aniline derivative used in the manufacture of the dye palatine fast yellow; it is also registered as a selective, low-volume-use (< 45 kg/yr) avicide. Three in vitro mutagenicity tests of CPT-HCl were performed according to methods recommended by the U.S. Environmental Protection Agency (EPA): the Ames/Salmonella assay, the Chinese hamster ovary/hypoxanthine-guanine phosphoribosyl-transferase (CHO/HPRT) mammalian cell forward gene mutation assay, and the CHO chromosome aberration assay. CPT-HCl did not display mutagenic activity using the Ames/Salmonella or CHO/HPRT assays. However, CPT-HCl induced statistically significant, concentration-dependent, metabolically activated increases in the proportion of aberrant cells and aberrations/cell in cultured CHO cells. Results are suggestive of minimal mutagenicity effects associated with exposure to anilines and their derivatives.

In vivo mutagenicity studies with iodinated glycerol azeo.

Previous studies have shown that iodinated glycerol azeo is positive in a number of in vitro mutagenicity assays including the Ames assay (TA100; TA1535), mouse lymphoma assay, Chinese hamster ovary (cytogenetic) assay and in one in vivo study, the sex-linked-recessive-lethal assay in Drosophila. Prior studies have also shown that the drug is negative in the mouse micronucleus assay. We now report that the drug is also negative for mutagenic activity in a number of other in vivo tests. Single intraperitoneal doses of 25, 125 and 250 mg/kg were without effect in the rat bone marrow chromosomal aberration assay. Single oral doses of 30, 75, 150 and 300 were negative in the rat hepatocyte DNA-repair assay. Single intraperitoneal doses of 30 and 100 mg/kg were without effect in the sister chromatid exchange (SCE) assay in the mouse. Statistically significant effects were seen at 200 and 300 mg/kg in the initial SCE assay and at 300 and 350 mg/kg in the confirmatory SCE assay. The rationale for considering the SCE results to be anomalous and thus not relative to the overall safety evaluation of the drug is presented.

Multiple-endpoint mutagenesis with Chinese hamster ovary (CHO) cells: evaluation with eight carcinogenic and non-carcinogenic compounds.

Previously, we have shown that Chinese hamster ovary (CHO) cells are useful for quantifying chemical-induced gene mutations. We have defined the conditions of a Multiplex CHO System which permits determination of mutagen-induced chromosome aberration, and sister chromatid exchange (SCE) in addition to cytotoxicity and gene mutation in the same treated culture. This allows us to extend the spectrum of quantitative mutagenesis to include clastogenic endpoints. In the present study, we used four carcinogenic/noncarcinogenic pairs to validate the relative utility and sensitivity of each endpoint, and to study the interrelationship of these four distinct biological effects. These compounds include the direct-acting carcinogens N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), ICR 170 and their noncarcinogenic analogue N-methyl-N'-nitroguanidine (MNG) and ICR 170-OH, and the procarcinogens benzo[a]pyrene (B[a]P) and dimethylnitrosamine (DMN) and their noncarcinogenic analogues pyrene and dimethylamine (DMA) respectively. A rat liver homogenate preparation (S9) was used to assay for the biological activities of procarcinogens. Under our experimental conditions, we observed that carcinogens DMN, B[a]P, MNNG and ICR 170, but not their noncarcinogenic counterparts, showed all four biological effects. Our studies with these chemicals showed that cytotoxicity does not necessarily correlate with any of the genetic endpoints. On a molar basis, noncarcinogens, pyrene and ICR 170-OH show similar toxicity to carcinogens B[a]P and ICR 170, respectively. The other two non-carcinogenic analogues, DMA and MNG, exhibit minimal toxicity at concentrations 10-1,000 times higher than cytotoxic concentrations of the corresponding carcinogens, DMN and MNNG. In general, gene mutation and SCE are more sensitive than chromosome aberration assay. The gene mutation assay is more specific than SCE and chromosome aberration assays since none of the noncarcinogens exhibit a detectable response in the gene mutational assay. ICR 170 and MNNG are much more active than B[a]P and DMN as ranked on a molar basis. These results indicate that the Multiplex CHO System is capable of discriminating divergent structural classes of carcinogenic and noncarcinogenic compounds, such as the eight chemicals chosen for our study.

Cytotoxicity and mutagenicity of dimethylnitrosamine in mammalian cells (CHO/HGPRT system); enhancement by calcium phosphate.

The cytotoxicity and mutagenicity of dimethylnitrosamine (DMN) was determined in the CHO/HGPRT system. Metabolic activation of the promutagen was achieved by use of liver homogenate supernatant (S9) prepared from Aroclor 1254-induced Sprague-Dawley rats. The cytotoxic and mutagenic effects of DMN were enhanced by the inclusion of calcium chloride in the incubation mix, and this enhancement was dependent on the presence of sodium phosphate. Under conditions that yielded maximal activity (10 mM calcium chloride, 10 mM magnesium chloride, 50 mM sodium phosphate), an apparent calcium phosphate precipitate was observed. DMN activity increased with increasing amounts of S9 protein over the range of 0.3-3.0 mg/ml in the S9 mix and appeared to plateau at higher concentrations. The mutagenicity of DMN can be described as 110 mutants/10(6) cells per mM DMN per mg/ml S9 protein per hour.

Induction of chromosomes aberrations, sister chromatid exchanges, and specific locus mutations in Chinese hamster ovary cells by 5-bromodeoxyuridine.

The induction of cytotoxicity, growth inhibition, specific locus mutations, and cytological alterations such as micronuclei, chromosome/chromatid aberrations, and sister chromatid exchanged by 5-bromodeoxyuridine (BudR) in Chinese hamster ovary cells was determined. BudR shows concentration-dependent increases in cytological alterations over the range of 5-500 muM, but it is mutagenic only at concentrations greater than 50 muM.

A quantitative assay of mutation induction at the hypoxanthine-guanine phosphoribosyl transferase locus in Chinese hamster ovary cells (CHO/HGPRT system): utilization with a variety of mutagenic agents.

The induction of mutation by a variety of mutagens has been measured utilizing the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in Chinese hamster ovary (CHO) cells (CHO/HGPRT) system). These mutagens include physical agents such as UV light and X-rays, and chemicals such as alkylating agents, ICR-191, and metallic compounds. This system can also be modified for study of the mutagenicity of promutagens such as dimethylnitrosamine (DMN) which require biotransformation for mutagenic action, either through the addition of a rat liver microsomal activation preparation or through a host-mediated activation step using Balb/c athymic mice.