Mammalian Cell Mutagenesis Assays Research Articles

Safety assessment of aditoprim acute, subchronic toxicity and mutagenicity studies.

Aditoprim (ADP), a new developed dihydrofolate reductase (DHFR) inhibitor, has great potential in clinical veterinary medicine because of its greater pharmacokinetic properties than structural analogs. Preclinical toxicology studies were performed to assess the safety of ADP including an acute oral toxicity test, a subchronic toxicity test and five mutagenicity tests. In the acute oral toxicity test, ADP was administered singly by oral gavage to Wistar rats and Kunming mice. The LD50 calculated was 1400 mg kg(-1) body weight (BW) day(-1) in rats and 1130 mg kg(-1) BW day(-1) in mice. In a subchronic study, Wistar rats were administered ADP at dose levels of 0, 20, 100 and 1000 mg kg(-1) diet for 90 days. Significant decreases were observed on body weight and food efficiency in the high-dose group. Treatment-related changes in clinical serum biochemistry were found in the medium- and high-dose groups. Significant increases in the relative weights of livers and kidneys in females and testis in males in the 1000 mg kg(-1) diet, and significant decrease in relative weights of livers in males in the 100 mg kg(-1) diet were noted. Histopathological observations revealed that the 1000 mg kg(-1) ADP diet could induce lymphocytic infiltration and hepatocytic necrosis near the hepatic portal area. The genotoxicity of ADP was negative in tests, such as the bacterial reverse mutation assay, mice bone marrow erythrocyte micronucleus assay, in vitro chromosomal aberration test, in vitro cho/hgprt mammalian cell mutagenesis assay and mice testicle cells chromosome aberration. Based on the subchronic study, the no-observed-adverse-effect level for ADP was a 20 mg kg(-1) diet, which is about 1.44-1.53 mg kg(-1) BW day(-1) in rats.

Integration of in vivo and in vitro approaches to characterize the toxicity of Antalarmin, a corticotropin-releasing hormone receptor antagonist

Non-clinical studies were conducted to evaluate the toxicity of Antalarmin, a corticotropin-releasing hormone type 1 receptor antagonist being developed for therapy of stress-related pathologies. Antalarmin was not genotoxic in bacterial mutagenesis assays, mammalian cell mutagenesis assays, or in vivo DNA damage assays. In a 14-day range-finding study in rats, Antalarmin doses ≥500 mg/kg/day (3000 mg/m 2/day) induced mortality. In a 90-day toxicity study in rats, no gross toxicity was seen at doses of 30, 100, or 300 mg/kg/day (180, 600, or 1800 mg/m 2/day, respectively). Antalarmin (300 mg/kg/day) induced mild anemia, increases in serum γ-glutamyl transferase activity, and microscopic hepatic pathology (bile duct hyperplasia and epithelial necrosis, periportal inflammation). Microscopic renal changes (cortical necrosis, inflammation, hypertrophy, nephropathy) were observed in rats at all Antalarmin doses. In a 14-day range-finding study in dogs, Antalarmin doses ≥50 mg/kg/day (1000 mg/m 2/day) induced repeated emesis and bone marrow suppression. In a 90-day toxicity study in dogs, Antalarmin (4, 8, or 16 mg/kg/day (80, 160, or 320 mg/m 2/day, respectively)) induced bone marrow and lymphoid depletion, but no gross toxicity. Comparative in vitro studies using rat, dog, and human neutrophil progenitors demonstrated that canine bone marrow cells are highly sensitive to Antalarmin cytotoxicity, while rat and human bone marrow cells are relatively insensitive. As such, the bone marrow toxicity observed in dogs is considered likely to over-predict Antalarmin toxicity in humans. The hepatic and renal toxicities seen in rats exposed to Antalarmin identify those tissues as the most likely targets for Antalarmin toxicity in humans.

Cytotoxicity and mutagenicity of Kevlar ®: an in vitro evaluation

Toxicity and mutagenicity of Kevlar ®49 (PPPT; poly- para-phenylene-terephthalamide) was tested in six strains of Salmonella typhimurium (Ames test; TA97, TA98, TA100, TA102, TA1535, TA1537) with and without an external metabolic activation system (S9), as well as in a mammalian cell mutagenesis assay using V79 Chinese hamster cells. For the Ames test, liquid preincubation, which is considered particularly sensitive, was used. The cells were incubated for 24 h at a temperature of 37 °C either directly with Kevlar49 or with ethanol- or chloroform-extracted Kevlar49. The experiments were performed at least twice. The Ames test with six different Salmonella typhimurium strains featuring either base pair substitution or frameshift mutations revealed no cytotoxic or mutagenic activity of Kevlar49. In the mammalian cell mutagenesis assay, using 8-azaguanine (AG) as a selective agent, Kevlar49 was also devoid of cytotoxic or mutagenic activity. Both tests have to be regarded as an initial exploratory screening due to the chosen testing conditions and should be supplemented by tests at different temperatures.

Genetic toxicology studies in SALATRIM structured triacylglycerols. 2. Lack of genetic damage in in vitro mammalian cell assays and the in vivo micronucleus assay

The SALATRIM family of triacylglycerols differs from other fats in the ratio of short-chain fatty acids (SCFA) to long-chain fatty acids (LCFA) and in that stearic acid is the major LCFA. These fats have caloric availability values (4.5-6 kcal/g) lower than that of corn oil (9 kcal/g). SALATRIM 23CA Lot A014, a typical SALATRIM fat, was tested in vitro mammalian cell genotoxicity assays including the chromosomal aberration, unscheduled DNA synthesis, and HPRT mammalian cell mutagenesis assays. Corn oil also was tested as a reference fat. Both the SALATRIM fat and corn oil were negative in the three assays. SALATRIM 234CA lot A019 and SALATRIM 234CS lot A018 were tested in the in vivo bone marrow micronucleus assay. Rats received these SALATRIM fats or corn oil at 10 % (w/w) in the diet for 13 weeks. Both fats were negative in this assay. The data confirm the prediction that SALATRIM fats lack genotoxic potential.

Analysis of metal-induced mutations altering the expression or structure of a retrovial gene in a mammalian cell line

Carcinogenic metal compounds, with the exception of chromium(VI), have been found to be poorly mutagenic in both prokaryotic and mammalian cell mutagenesis assays, yet they are clearly clastogenic (Hansen and Stern, 1984). Thus, the role of metals as initiators in carcinogenesis has been difficult to delianeate. In an effort to develop a model system capable of assaying DNA damage caused by carcinogenic metals, we have investigated the role of NiCl 2, CdCl 2, Na 2CrO 4, and NMU in a murine sarcoma virus-infected mammalian cell line in which expression of the retroviral v- mos gene is growth-temperature regulated. This cell line, designated 6m2, contains a single-copy, stably integrated, mutant Moloney murine sarcoma virus DNA (designated MuSVts110) and is temperature sensitive for morphological transformation due to a conditionally defective viral RNA-splicing event that in turn regulates expression of the viral transforming gene. Mutations affecting the viral DNA in 6m@ cells can be detected if these alterations lead to changes in the structure or expression of the transforming protein encoded by the MuSVts100 v- mos gene. Analysis of the viral proteins from 6m2 ‘revertant’ cell lines (as defined by reversion to the transformed phenotyped at all growth temperatures) selected after treatment with the above agents showed that NiCl 2, NMU, and Na 2CrO 4 each induced a different yet specific type of mutation. NiCl 2 and NMU each altered the temperature sensitivity of viral RNA splicing, possibly due to base substitution mutations, but did so to distinctly different extents. Na 2CrO 4 affected the structure of the viral proteins by inducing what appear to be short frameshift mutations that resulted in the temperature-dependent translation of a novel virus-encoded transforming protein, P100 gag-mos. CdCl 2 also induced frameshift mutations but, in one case, induced a mutation which may result from a deletion of about 300 bases within the MuSVts110 DNA.

Potent anti-viral 5-(2-bromovinyl) uracil nucleosides are inactive at inducing gene mutations in Salmonella typhimurium and V79 Chinese hamster cells and unscheduled DNA synthesis in primary rat hepatocytes.

(E)-5-(2-bromovinyl)-2'-deoxyuridine (BDVU), one of the most potent and selective anti-herpes agents described to date, and its close congeners (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil (BVaraU) and (E)-5-(2-bromovinyl)uracil (BVU), as well as the reference compounds 5-iodo-2'-deoxyuridine (IDU) and 5-trifluoro-2'-deoxythymidine (TFT) were examined for their genotoxic potential. With the exception of a weak activity of TFT in the newly developed strain TA 102, none of the compounds was active in a bacterial cell mutagenesis (Salmonella/microsome) assay. Nor did they induce DNA repair (unscheduled DNA synthesis) in primary rat hepatocytes. In a mammalian cell mutagenesis assay using V79 Chinese hamster cells, the reference compounds IDU and TFT proved highly cytotoxic and mutagenic, whereas BVDU, BVaraU and BVU were neither cytotoxic nor mutagenic.

Potent antiviral 2'-fluoro-arabinosyl pyrimidine nucleosides: lack of mutagenic activity.

The carcinogenicity of many drugs, such as antitumor agents, is a subject of growing concern. The newly developed pyrimidine nucleosides, 2'-fluoro-5-iodo-1-beta-D-arabinofuranosylcytosine (FIAC) and 2'-fluoro-1-beta-D-arabinofuranosyl-5-methyluracil (FMAU), have shown potent anti-herpes virus activity in tissue cultures, laboratory animals and man and an activity to inhibit the growth of certain tumor cell lines in vitro. Radioactivity of 14C-labeled FIAC and FMAU is incorporated into the DNA of normal and neoplastic mammalian tissues. However, we now report that FIAC and FMAU are inactive in a bacterial mutagenesis assay (Salmonella-microsome test) and in a mammalian cell mutagenesis assay employing V79 Chinese hamster cells in vitro. Both agents did not induce unscheduled DNA synthesis in primary Wistar rat hepatocytes in vitro.

Computation of test results in a mammalian cell mutagenesis assay

A set of TI-59 calculator programs is presented for use in mammalian cell mutation assays. Applicability of the programs is illustrated by measurement of mutation at the HGPRT locus using Chinese hamster ovary cells. The programs calculate cloning efficiencies, mutation yield, and mutation frequencies. Intermediate data stored on magnetic cards are used by additional subprograms to calculate standard statistical parameters and to perform significance tests using the t- and F-distributions.

Mutagenicity testing in mammalian cells: I. Derivation of a chinese hamster ovary cell line heterozygous for the adenine phosphoribosyltransferase and thymidine kinase loci

As a first step in the development of a multiple-marker, mammalian cell mutagenesis assay system, we have isolated a Chinese hamster ovary (CHO) cell line that is heterozygous for both the adenine phosphoribosyltransferase ( aprt) and thymidine kinase ( tk) loci. Presumptive aprt +/− heterozygotes with intermediate levels of APRT activity were selected from unmutagenized CHO cell populations on the basis of resistance to low concentrations of the adenine analog, 8-azaadenine. A functional aprt +/− heterozygote with ∼50% wild-type APRT activity was subsequently used to derive sublines that were also heterozygous for the tk locus. Biochemical and genetic characterization of one such subline, CHO-AT3-2, indicated that it was indeed heterozygous at both the aprt and tk loci. CHO-AT3-2 cells permitted single-step selection of mutants resistant to 8-azaadenine or 5-fluorodeoxyuridine, allowing quantitation and direct comparison of mutation induction at the autosomal aprt or tk loci, as well as in the gene involved in ouabain resistance or at the X-linked, hypoxanthine-guanine phosphoribosyltransferase ( hgprt) locus. Significant dose-dependent increases in mutation frequency were observed for all 4 genetic markers after treatment of CHO-AT3-2 cells with ethyl methanesulfonate.