Induction of deletion mutations by methoxyacetaldehyde in Chinese hamster ovary (CHO)-AS52 cells

Mutation analyses of a series of TNT-related compounds using the CHO-hprt assay

Trinitrotoluene (TNT) and related compounds were tested for induction of mutation in the CHO-hprt mutation assay. The parent compound, TNT, was consistently found to be mutagenic at concentrations above 40 microg ml(-1), whether or not S9 activating enzymes were added. Five TNT metabolites gave statistically significant but small increases in mutation frequency over solvent controls: 4-amino-2,6 dinitrotoluene, 2,4',6,6'-tetranitro-2',4-azoxytoluene, 2,2',6,6'-tetranitro-4,4'-azoxytoluene, 2',4,6,6'-tetranitro-2,4'-azoxytoluene and triaminotoluene. Clear dose-response relationships could not be established for the mutagenic response of these compounds. They are considered as very weak mutagens in this mammalian test system. Five compounds did not produce statistically significant mutation frequencies at the levels tested: 2-amino-4,6-dinitrotoluene, 2,4-diamino-6-nitrotoluene, 1,3,5-trinitrobenzene, 2,6-diamino-4-nitrotoluene and 4,4',6,6'-tetranitro-2,2'-azoxytoluene. The results indicate that none of the TNT metabolites tested pose a significant mutational health risk, at least as judged by the CHO-hprt assay.

Toxicity review of ethylene glycol monomethyl ether and its acetate ester

Ethylene glycol monomethyl ether (EGME) and its acetate ester (EGMEA) are highly flammable, colorless, moderately volatile liquids with very good solubility properties. They are used in paints, lacquers, stains, inks and surface coatings, silk-screen printing, photographic and photo lithographic processes, for example, in the semiconductor industry, textile and leather finishing, production of food-contact plastics, and as an antiicing additive in hydraulic fluids and jet fuel. EGME and EGMEA are efficiently absorbed by inhalation as well as via dermal penetration. Dermal absorption may contribute substantially to the total uptake following skin contact with liquids or vapours containing EGME or EGMEA. EGMEA is rapidly converted to EGME in the body and the two substances are equally toxic in animals. Therefore, the two substances should be considered as equally hazardous to man. Effects on peripheral blood, testes, and sperm have been reported at occupational exposure levels ranging between 0.4 and 10 ppm EGME in air, and with additional, possibly substantial, dermal exposure. Severe malformations and disturbed hematopoiesis have been linked with exposure to EGME and EGMEA at unknown, probably high, levels. Embryonic deaths in monkeys and impaired spermatogenesis in rabbits have been reported after daily oral doses of 12 and 25 mg per kg body weight, respectively. In several studies, increased frequency of spontaneous abortions, disturbed menstrual cycle, and subfertility have been demonstrated in women working in the semiconductor industry. The contribution of EGME in relation to other exposure factors in the semiconductor industry is unclear.

Effects of reactive oxygen species (ROS) modulators, TEMPOL and catalase, on methoxyacetaldehyde (MALD) -induced chromosome aberrations in Chinese hamster ovary (CHO)-AS52 cells

Methoxyacetaldehyde (MALD), a metabolite of 2-methoxyethanol, has been shown to be clastogenic and mutagenic in CHO-AS52 cells. PCR-based-deletion screening of MALD induced CHO-AS52 mutants indicates that MALD induces large deletion mutation. Since MALD has an aldehyde as its reactive functional group, it can react with aldehyde oxidase to produce superoxide. The generation of these reactive oxygen species (superoxide, hydrogen peroxide and hydroxyl radical) may be the mechanism for genotoxicity of MALD. In the present study, TEMPOL and catalase which are ROS modulators were used to study the effects on MALD-induced chromosome damage in CHO-AS52 cells. The results showed that neither TEMPOL nor catalase can protect cells from MALD-induced chromosome aberrations. Therefore, the generation of reactive oxygen species may not be the primary mechanism of action of MALD.

An investigation of bone marrow and testicular cells in vivo using the comet assay

The effects of the mutagens, cyclophosphamide (CP), ethyl methanesulphonate (EMS), bleomycin (BLM) and the testicular toxin ethylene glycol monomethyl ether (EGME) in bone marrow and testicular cells have been compared in the alkaline COMET assay. Sprague-Dawley rats were administered by gavage with 50, 100 and 150 mg/kg body weight (bw) of CP; 100, 200 and 300 mg/kg bw EMS; 50, 100 and 150 mg/kg bw BLM and 500, 1000 and 1500 mg/kg bw EGME. Effects were examined at week 2 after treatment for CP, EMS BLM and EGME and at weeks 5 and 6 for EGME. Bone marrow cells were removed and separated by aspiration of the femur and testicular cells by decapsulation of the testis, treating with collagenase followed by trypsin. Various statistical methods were used to analyse the data. For CP there was an increase in damage above control values for bone marrow at 50 mg/kg bw which decreased at 100 mg/kg bw, and there was mortality of the animals at 150 mg/kg bw. A similar response was found in the testicular cells. For EMS and BLM, there were only occasional slight increases in damage in bone marrow and testicular cells. Two studies were conducted with EGME. In the first, where effects were examined at week 2 after treatment, there was an increase in damage in bone marrow cells, but a larger response was observed in testicular cells. In the second study where effects were examined at weeks 5 and 6 after treatment, bone marrow and testicular cells were not affected. The overall results showed that damage persisted for 2 weeks after treatment with CP and EGME but not in weeks 5 and 6 for EGME. Various statistical methods were used to analyse the data. Statistically significant responses were produced after treatment with CP and EGME and were dose-related for EGME, but after treatment with EMS and BLM statistical increases were sporadic. These results suggest that the assay is useful for measuring DNA damage and its persistence, and for comparing the sensitivity of different target organs in vivo.