RESUMEN
We investigated the spindle inhibitory properties of six arsenicals differing in their methylation or oxidation state. Human lymphoblasts were exposed for 6 h to either sodium arsenate (NaAs(V)), sodium arsenite (NaAs(III)), monomethylarsonic acid (MMA(V)), monomethylarsonous acid (MMA(III)), dimethylarsinic acid (DMA(V)), or dimethylarsinous acid (DMA(III)). After exposure slides were prepared, and the mitotic indices (MI) were assessed. We also exposed tubulin directly to each arsenical and spectrophotometrically measured its effect on polymerization. NaAs(V) caused a small but significant increase in MI. MMA(V) also caused only a slight increase in MI that just reached statistical significance. In contrast, DMA(V) caused a significant increase in MI, producing approximately 75% the MI of demecolcine and approximately 4 times the MI of the control. NaAs(III) had no significant effect on MI and was quite toxic. MMA(III) induced more than a twofold increase in MI compared to the control, which was about 40% that caused by demecolcine. On a micromolar basis, MMA(III) was the most potent of the arsenicals tested. DMA(III) gave inconsistent results. None of the pentavalent arsenicals had a substantial effect (either inhibition or enhancement) on GTP-induced polymerization of tubulin. In contrast, NaAs(III) inhibited polymerization at concentrations of 1 mM and above and MMA(III) and DMA(III) at 10 microM and above. Taken together, these results present a complex picture of how arsenicals may affect cells. These studies demonstrate that the metabolites of arsenic are active not only as chromosome breaking and DNA damaging agents but can also interfere with cell division via tubulin disruption.
Asunto(s)
Arsénico/toxicidad , Linfocitos/efectos de los fármacos , Huso Acromático/efectos de los fármacos , Aneuploidia , Arsenicales , Arsenitos/toxicidad , Ácido Cacodílico/toxicidad , Células Cultivadas , Relación Dosis-Respuesta a Droga , Humanos , Metilación , Índice Mitótico , Compuestos Organometálicos/toxicidad , Oxidación-Reducción , Compuestos de Sodio/toxicidad , Relación Estructura-Actividad , Factores de Tiempo , Tubulina (Proteína)/metabolismo , Moduladores de Tubulina/toxicidadRESUMEN
Atrazine, simazine, and cyanazine are widely used preemergence and postemergence triazine herbicides that have made their way into the potable water supply of many agricultural communities. Although there are several contradictory genotoxicity studies in the literature, our previous in vitro studies with human lymphocytes showed that atrazine, simazine, and cyanazine did not induce sister chromatid exchanges (SCEs) or chromosome aberrations (CAs) up to the limits of solubility in aqueous medium using 0.5% dimethyl sulfoxide. To expand upon these results and to ensure that our in vitro findings could be replicated in an in vivo system, mice were treated with each triazine by two intraperitoneal injections, 24h apart. The animals were sacrificed and the bone marrow removed for micronucleus (MN) analysis, 24h after the last injection. Two to four independent trials were performed for MN analysis in polychromatic erythrocytes, and in some trials the spleen was removed, cultured, and analyzed for SCEs and CAs. None of the triazines investigated induced MN in the bone marrow, even at doses that caused significant bone marrow suppression and/or death. These results indicate that atrazine, simazine, and cyanazine are not genotoxic as measured by the bone marrow MN assay in mice following high dose exposures.
Asunto(s)
Atrazina/toxicidad , Células de la Médula Ósea/efectos de los fármacos , Herbicidas/toxicidad , Pruebas de Micronúcleos , Mutágenos/toxicidad , Simazina/toxicidad , Triazinas/toxicidad , Animales , Atrazina/administración & dosificación , Células de la Médula Ósea/patología , Células Cultivadas , Eritroblastos/efectos de los fármacos , Eritroblastos/patología , Femenino , Herbicidas/administración & dosificación , Inyecciones Intraperitoneales , Ratones , Ratones Endogámicos C57BL , Micronúcleos con Defecto Cromosómico/efectos de los fármacos , Mutágenos/administración & dosificación , Simazina/administración & dosificación , Bazo/efectos de los fármacos , Bazo/patología , Triazinas/administración & dosificaciónRESUMEN
Atrazine, simazine, and cyanazine are widely used pre-emergence and post-emergence triazine herbicides that have made their way into the potable water supply of many agricultural communities. Because of this and the prevalence of contradictory cytogenetic studies in the literature on atrazine, simazine, and cyanazine, a series of in vitro experiments was performed to investigate the ability of these three triazines to induce sister chromatid exchanges (SCEs) and chromosome aberrations (CAs) in human lymphocyte cultures. Our results showed that all three triazines failed to produce any significant increases in SCEs or CAs up to the limits of solubility [using 0.5% dimethyl sulfoxide (DMSO)]. Our results are discussed in light of contradictory results in the literature.
Asunto(s)
Aberraciones Cromosómicas , Herbicidas/toxicidad , Intercambio de Cromátides Hermanas/efectos de los fármacos , Atrazina/toxicidad , Citogenética , Humanos , Técnicas In Vitro , Linfocitos/efectos de los fármacos , Simazina/toxicidad , Triazinas/toxicidadRESUMEN
3,4-epoxy-1-butene (EB), a primary metabolite of butadiene, is a direct-acting "S-dependent" genotoxicant that can induce sister chromatid exchanges (SCEs) and chromosome aberrations (CAs) in cycling cells in vitro. However, EB is almost inactive when splenic or peripheral blood lymphocytes are exposed at the G(0) stage of the cell cycle. To investigate whether repair of DNA lesions is responsible for the lack of cytogenetic responses seen after G(0) treatments, we used cytosine arabinoside (ara-C) to inhibit DNA polymerization during DNA repair. If enough repairable lesions are present, double-strand breaks should accumulate and form chromosome-type ("S-independent") deletions and exchanges. This is exactly what occurred. EB induced chromosome deletions and dicentrics at the first division following treatment, when the EB exposure was followed by ara-C. Without ara-C treatment, there was no induction of CAs. These experiments indicate that the relatively low levels of damage induced by EB in G(0) lymphocytes are removed by DNA repair prior to DNA synthesis and thus, before the production of SCEs or chromatid-type aberrations.
Asunto(s)
Compuestos Epoxi/toxicidad , Mutágenos/toxicidad , Ciclo Celular , Aberraciones Cromosómicas , Citarabina/farmacología , ADN/biosíntesis , ADN/efectos de los fármacos , ADN/genética , Reparación del ADN/efectos de los fármacos , Humanos , Técnicas In Vitro , Linfocitos/citología , Linfocitos/efectos de los fármacos , Linfocitos/metabolismo , Fase de Descanso del Ciclo Celular , Intercambio de Cromátides Hermanas/efectos de los fármacosRESUMEN
To understand better the species differences in carcinogenicity caused by 1,3-butadiene (BD), we exposed G0 lymphocytes (either splenic or peripheral blood) from rats, mice and humans to 3, 4-epoxy-1-butene (EB) (20 to 931 microM) or 1,2:3,4-diepoxybutane (DEB) (2.5 to 320 uM), two of the suspected active metabolites of BD. Short EB exposures induced little measurable cytogenetic damage in either rat, mouse, or human G0 lymphocytes as measured by either sister chromatid exchange (SCE) or chromosome aberration (CA) analyses. However, DEB was a potent inducer of both SCEs and CAs in G0 splenic and peripheral blood lymphocytes. A comparison of the responses among species showed that the rat and mouse were approximately equisensitive to the cytogenetic damaging effects of DEB, but the situation for the human subjects was more complex. The presence of the GSTT1-1 gene (expressed in the erythrocytes) reduced the relative sensitivity of the lymphocytes to the SCE-inducing effects of DEB. However, additional factors also appear to influence the genotoxic response of humans to DEB. This study is the first direct comparison of the genotoxicity of EB and DEB in the cells from all three species.
Asunto(s)
Butadienos/toxicidad , Carcinógenos/farmacología , Compuestos Epoxi/toxicidad , Interfase/genética , Linfocitos/efectos de los fármacos , Animales , Ciclo Celular/efectos de los fármacos , Ciclo Celular/genética , Aberraciones Cromosómicas/genética , Eritrocitos/enzimología , Genotipo , Glutatión Transferasa/genética , Humanos , Ratones , Pruebas de Mutagenicidad , Ratas , Análisis de Regresión , Intercambio de Cromátides Hermanas/efectos de los fármacos , Intercambio de Cromátides Hermanas/genéticaRESUMEN
A pilot biomarker study was conducted to investigate the feasibility of using the hypoxanthine guanine phosphoribosyltransferase (HPRT) gene in peripheral blood lymphocytes as a biomarker for detecting genetic effects of arsenic exposure. Blood and urine samples were obtained from workers highly exposed to arsenic in a copper roasting plant in Antofagasta, Chile. Individuals were classified according to their job titles into three potential exposure groups: high, medium, and low. To confirm exposure, arsenic concentration was determined in urine samples. The HPRT mutant frequencies were measured in lymphocytes from 15 individuals ranging in age from 24 to 66 years. The mean mutant frequencies for the three exposure groups were: low (9 x 10(-6)), medium (11 x 10(-6)), and high (24 x 10(-6)). An increased mutant frequency was observed in the highly exposed group, but the response was so slight that it is not likely that this assay will be capable of providing dose-response information across a range of lower, more typical environmental arsenic levels.
Asunto(s)
Arsénico/toxicidad , Hipoxantina Fosforribosiltransferasa/efectos de los fármacos , Hipoxantina Fosforribosiltransferasa/genética , Mutación , Exposición Profesional , Anciano , Biomarcadores , Chile , Aberraciones Cromosómicas , Análisis Mutacional de ADN , Relación Dosis-Respuesta a Droga , Genética de Población , Humanos , Linfocitos/efectos de los fármacos , Linfocitos/fisiología , Masculino , Metalurgia , Persona de Mediana Edad , Proyectos PilotoRESUMEN
The disinfection of water, required to make it safe for human consumption, leads to the presence of halogenated organic compounds. Three of these carcinogenic 'disinfection by-products', dichloroacetic acid (DCA), trichloroacetic acid (TCA) and chloral hydrate (CH) have been widely evaluated for their potential toxicity. The mechanism(s) by which they exert their activity and the steps in the etiology of the cancers that they induce are important pieces of information that are required to develop valid biologically-based quantitative models for risk assessment. Determining whether these chemicals induce tumors by genotoxic or nongenotoxic mechanisms (or a combination of both) is key to this evaluation. We evaluated these three chemicals for their potential to induce micronuclei and aberrations as well as mutations in L5178Y/TK +/- (-)3.7.2C mouse lymphoma cells. TCA was mutagenic (only with S9 activation) and is one of the least potent mutagens that we have evaluated. Likewise, CH was a very weak mutagen. DCA was weakly mutagenic, with a potency (no. of induced mutants/microgram of chemical) similar to (but less than) ethylmethanesulfonate (EMS), a classic mutagen. When our information is combined with that from other studies, it seems reasonable to postulate that mutational events are involved in the etiology of the observed mouse liver tumors induced by DCA at drinking water doses of 0.5 to 3.5 g/l, and perhaps chloral hydrate at a drinking water dose of 1 g/l. The weight-of-evidence for TCA suggest that it is less likely to be a mutagenic carcinogen. However, given the fact that DCA is a weak mutagen in the present and all of the published studies, it seems unlikely that it would be mutagenic (or possibly carcinogenic) at the levels seen in finished drinking water.
Asunto(s)
Hidrato de Cloral/toxicidad , Ácido Dicloroacético/toxicidad , Desinfectantes/toxicidad , Leucemia L5178/genética , Mutágenos/toxicidad , Ácido Tricloroacético/toxicidad , Purificación del Agua , Animales , Aberraciones Cromosómicas , Ratones , Pruebas de Mutagenicidad , Timidina Quinasa/genética , Células Tumorales Cultivadas/efectos de los fármacosRESUMEN
Arsenic is one of the few identified human carcinogens that has yet to be shown to cause cancer in rodents when the standard bioassay protocols are used. The reasons for this apparent interspecies difference are unclear but may be related to differences between humans and rodents in their detoxification capabilities. Detoxification of arsenic may occur through a methylation pathway. If, in fact, methylation does detoxify arsenic, one would predict that the methylated arsenicals might be less genotoxic than the inorganic arsenicals. To evaluate the hypothesis that the inorganic arsenicals are more mutagenic than the organic arsenicals, we tested sodium arsenite, sodium arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) for their relative mutagenic and clastogenic potentials. We used the L5178Y/TK+/- mouse lymphoma assay which allows the detection of chemicals inducing a broad spectrum of different types of genetic damage. Sodium arsenite and sodium arsenate were active at concentrations of 1-2 micrograms/ml and 10-14 micrograms/ml, respectively. MMA was active between 2500-5000 micrograms/ml; while DMA required almost 10000 micrograms/ml to induce a genotoxic response. The organic arsenicals are thus much less potent as mutagenic agents than the inorganic arsenicals. All four of these arsenicals appear to act by mechanisms that cause chromosomal mutations.
Asunto(s)
Arsénico/toxicidad , Aberraciones Cromosómicas , Linfoma/genética , Venenos/toxicidad , Animales , Arsénico/química , Humanos , Metilación , Ratones , Células Tumorales CultivadasRESUMEN
As a first step in investigating the genotoxic effects of the principal metabolites of 1,3-butadiene (BD) in both rats and mice, splenocytes (which have little mixed function oxidase activity) from each specimen were exposed to a series of concentrations of either 3,4-epoxy-1-butene (EB) (20 to 931 microM) or 1,2:3,4-diepoxybutane (DEB) (2.5 to 160 microM) for 1 h. The splenocytes were then washed, cultured, and stimulated to divide with concanavalin A, and metaphases were analyzed for the induction of sister chromatid exchanges (SCEs) and chromosome aberrations (CAs). In addition, cells from some experiments were taken after exposure but before culture, and subjected to the single cell gel (SCG) assay to measure DNA damage in the form of DNA strand breakage and/or alkaline-labile sites. Initial studies indicate that EB does not induce cytogenetic damage in either rat or mouse G0 splenocytes. However, DEB was an extremely potent SCE- and CA-inducer in both species with no species differences apparent. Neither DEB nor EB produced any statistically significant DNA-damaging effects as measured by the SCG assay.
Asunto(s)
Aberraciones Cromosómicas , Compuestos Epoxi/toxicidad , Mutágenos/toxicidad , Intercambio de Cromátides Hermanas , Animales , Ciclo Celular/efectos de los fármacos , Células Cultivadas , Masculino , Ratones , Ratas , Especificidad de la Especie , Bazo/citología , Bazo/efectos de los fármacosRESUMEN
Male B6C3F1 mice (8 weeks of age) were exposed by inhalation to divinylbenzene-55 (DVB-55), at target concentrations of 0, 25, 50 and 75 ppm for 6 h per day for 3 days. Following exposure the animals were killed blood smears were prepared for micronucleus (MN) analysis, and the spleens were removed and cultured for sister chromatid exchange (SCE) and chromosome aberration (CA) analyses. DVB-55 induced a dose dependent increase in SCE with the two highest doses reaching statistical significance. Similarly, there was a statistically significant although less pronounced increase in the frequency of CAs in splenocytes and MN in polychromatic erythrocytes. There was no indication of toxicity as measured by cell cycle kinetics in the splenocytes or the percentage of polychromatic erythrocytes in the peripheral blood smears. Thus, DVB-55 appears to be a weak genotoxicant in vivo.
Asunto(s)
Aberraciones Cromosómicas , Compuestos de Vinilo/toxicidad , Administración por Inhalación , Animales , Relación Dosis-Respuesta a Droga , Masculino , Ratones , Intercambio de Cromátides Hermanas/efectos de los fármacos , Estireno , Estirenos/toxicidad , Compuestos de Vinilo/administración & dosificaciónRESUMEN
PURPOSE: To compare the effect of thermocycling on the microleakage of conventional and resin modified glass ionomer restorative materials. MATERIALS AND METHODS: Class V preparations, centered on the CEJ, were prepared on the lingual and facial surfaces of 30 extracted human third molar teeth. Preparations were conditioned and restored randomly on one surface with Ketac-Fil and on the other surface with Photac-Fil. Restorations were protected during curing, finishing, and storage with Ketac-Glaze. Specimens were aged in room temperature distilled water for 7 days. Half of the specimens were thermocycled for 2,500 cycles in 5 degrees-55 degrees water baths with 5-second dwell times. All specimen apices were sealed with red compound, occlusal fissures sealed with pit/fissure sealant, and surfaces painted to within 1.5 mm of restoration margins with red nail polish. Specimens were stained with 5% methylene blue, invested in orthodontic resin, and sectioned faciolingually. The percentage of dye penetration along the tooth restoration interface was measured with a digital imaging system. RESULTS: Statistical analysis showed that neither thermocycling or type of material had a significant effect on dye penetration (P > 0.5).
Asunto(s)
Filtración Dental , Cementos de Ionómero Vítreo , Cementos de Resina , Análisis de Varianza , Adaptación Marginal Dental , Investigación Dental/métodos , Cementos de Ionómero Vítreo/química , Calor , Humanos , Maleatos , Ensayo de Materiales/métodos , Resinas Sintéticas , Manejo de Especímenes , Agua/químicaRESUMEN
3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) was tested without exogenous activation in L5178Y/TK+/(-)-3.7.2C mouse lymphoma cells for mutation at the thymidine kinase locus and for clastogenicity. At a concentration of 0.75 micrograms/ml, the induced mutant frequency was 1027 per 10(6) survivors (survival = 11%). A concentration-related increase of large and small colony mutants was observed, but the majority of the MX induced mutants formed small colonies, consistent with the positive clastogenic response that was observed. MX primarily induced chromatid breaks and rearrangements (30 chromatid and 4 chromosome aberrations per 100 cells) at the 0.75 microgram/ml dose. These studies indicate that MX induces a broad spectrum of genetic damage.
Asunto(s)
Furanos/toxicidad , Mutágenos/toxicidad , Contaminantes del Agua/toxicidad , Animales , Células CHO , Células Clonales , Cricetinae , Linfoma , Ratones , Timidina Quinasa/genética , Timidina Quinasa/metabolismo , Células Tumorales CultivadasRESUMEN
Trichloroethylene (TCE) (CAS No. 79-01-6) is an industrial solvent used in degreasing, dry cleaning, and numerous other medical and industrial processes. Controlled inhalation studies were performed using male C57BL/6 mice and CD rats to determine if TCE can induce cytogenetic damage in vivo. Animals were exposed in groups of five to target concentrations of either 0, 5, 500, or 5000 ppm TCE for 6 h. Tissue samples were taken between 18 and 19 h post exposure. Peripheral blood lymphocytes (PBLs) in rats and splenocytes in mice were cultured and analyzed for the induction of sister-chromatid exchanges, chromosome aberrations, and micronuclei (MN) in cytochalasin B-blocked binucleated cells. Bone marrow polychromatic erythrocytes (PCEs) were analyzed for MN. The only positive response observed was for MN in rat bone marrow PCEs. TCE caused a statistically significant increase in MN at all concentrations, inducing an approximate fourfold increase over control levels at 5000 ppm. TCE was also cytotoxic in rats, causing a significant concentration-related decrease in the ratio of PCEs/normochromatic erythrocytes. This study indicates that there may be species-specific cytogenetic effects attributed to TCE inhalation exposure. In follow-up studies, CD rats were exposed for 6 h/day over 4 consecutive days to either 0, 5, 50 or 500 ppm TCE. No statistically significant concentration-related increases in cytogenetic damage were observed. While the MN frequencies in the 4-day study were comparable to those at the equivalent concentrations in the 1-day study, they were not significantly elevated due to an unusually high MN frequency in the controls. A subsequent replication of the 1-day 5000 ppm TCE exposure with rats again showed a highly significant increase in MN frequencies compared to concurrent controls.
Asunto(s)
Aberraciones Cromosómicas , Micronúcleos con Defecto Cromosómico/efectos de los fármacos , Intercambio de Cromátides Hermanas , Tricloroetileno/toxicidad , Administración por Inhalación , Animales , Relación Dosis-Respuesta a Droga , Masculino , Ratones , Ratones Endogámicos C57BL , Ratas , Ratas Endogámicas , Factores de Tiempo , Tricloroetileno/administración & dosificaciónRESUMEN
Phosphine (PH3) is a highly toxic grain fumigant that can be produced from the reaction of metal phosphides with water. To determine the in vivo cytogenetic effects of inhalation of PH3, male CD-1 mice were exposed to either 0, 5, 10, or 15 ppm target concentrations of PH3 for 6 hr. Twenty hours after the termination of exposure, the spleens of the mice were removed, macerated, and the splenocytes cultured for analyses of sister chromatid exchanges, chromosome aberrations, and micronuclei in cytochalasin B-induced binucleated cells. In addition, bone marrow smears were made for the analysis of micronuclei in polychromatic erythrocytes. No increase in any of the cytogenetic endpoints was found at any of the concentrations examined. The only statistically significant response was a concentration-related slowing of the cell cycle in the splenocytes.
Asunto(s)
Ciclo Celular/efectos de los fármacos , Aberraciones Cromosómicas , Insecticidas/toxicidad , Mutágenos/toxicidad , Fosfinas/toxicidad , Administración por Inhalación , Animales , Células Cultivadas/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Eritrocitos/efectos de los fármacos , Linfocitos/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos , Pruebas de Micronúcleos , Mutágenos/administración & dosificación , Fosfinas/administración & dosificación , Intercambio de Cromátides Hermanas , Bazo/citología , Bazo/efectos de los fármacos , Factores de TiempoRESUMEN
The L5178Y mouse lymphoma assay was used to examine the potential mutagenicity of three halogenated pyridine compounds. Position effects of the halogen moiety and the role of metabolic activation were analyzed based on induced mutant frequency, gross chromosome aberrations, and micronuclei. Without activation, 2-chloropyridine, 3-chloropyridine, and 2-chloro-5-trifluoromethylpyridine produced a small increase in mutant frequency; only the 2-chloropyridine activity was significantly increased with activation. All three compounds were also clastogenic as demonstrated by increases in chromosome aberrations and micronuclei (except for 2-chloro-5-trifluoromethylpyridine which did not induce micronuclei either with or without activation).
Asunto(s)
Aberraciones Cromosómicas , Hidrocarburos Halogenados/toxicidad , Pruebas de Mutagenicidad , Mutágenos/toxicidad , Piridinas/toxicidad , Animales , Linfoma , Ratones , Pruebas de Micronúcleos , Células Tumorales Cultivadas/efectos de los fármacosRESUMEN
The data for the in vivo genotoxicity of styrene (STY) are equivocal. To evaluate the clastogenicity and sister-chromatid exchange (SCE)-inducing potential of STY in vivo under carefully controlled conditions, B6C3F1 female mice were exposed by inhalation for 6 h/day for 14 consecutive days to either 0, 125, 250 or 500 ppm STY. One day after the final exposure, peripheral blood, spleen, and lungs were removed and cells were cultured for the analysis of micronucleus (MN) induction using the cytochalasin B-block method, chromosome breakage, and SCE induction. Peripheral blood smears were also made for scoring MN in erythrocytes. There was a significant concentration-related elevation of SCE frequency in lymphocytes from the spleen and the peripheral blood as well as in cells from the lung. However, no statistically significant concentration-related increases were found in the frequency of chromosome aberrations in the cultured splenocytes or lung cells, and no significant increases in MN frequencies were observed in binucleated splenocytes or normochromatic erythrocytes in peripheral blood smears.
Asunto(s)
Aberraciones Cromosómicas , Estirenos/toxicidad , Administración por Inhalación , Animales , Citocalasina B/farmacología , Femenino , Ratones , Pruebas de Micronúcleos , Pruebas de Mutagenicidad , Intercambio de Cromátides Hermanas , Estireno , Estirenos/administración & dosificaciónRESUMEN
A series of in vitro experiments were conducted to determine if there are innate differences in the sensitivity of peripheral blood lymphocytes (PBLs) from different mammalian species to clastogens. Mouse, rat, and human whole blood samples were exposed to either 0, 0.38, 0.75, 1.5, or 3.0 Gy x-radiation or 0, 5, 10, 20, 40, or 80 micrograms/ml bleomycin for 4 hr. Bromodeoxyuridine-containing cultures were initiated and the PBLs stimulated to divide with phytohemagglutinin. All cultures were harvested following a 3-hr colcemid treatment. Slides were made and differentially stained, and first-division metaphases were scored for chromosome aberrations. In the x-radiation studies human PBLs were significantly more sensitive than mouse PBLs which were in turn more sensitive than rat PBLs as measured by either the total percent aberrant cells or the number of dicentrics. Data from all three species could be fitted to a linear-quadratic model. Results with bleomycin suggest that the mouse and human PBLs are equally sensitive to the clastogenic effects of bleomycin. Both appeared to be more sensitive than the rat PBLs, but the variation between experiments was such that the results among species were not significantly different. These results indicate that there may be inherent differences in sensitivity among PBLs of mammalian species; however, more studies are needed to determine if the differences presented here hold for other agents.
Asunto(s)
Bleomicina/toxicidad , Pruebas de Mutagenicidad , Animales , Células Cultivadas , Humanos , Linfocitos/efectos de los fármacos , Linfocitos/efectos de la radiación , Masculino , Ratones , Ratones Endogámicos C57BL , Ratas , Especificidad de la EspecieRESUMEN
Over the past several years, we have been evaluating the mutagenicity and clastogenicity of compounds capable of Michael-type reactions. These compounds, including acrylamide, several acrylate and methacrylate esters, vinyl sulfones, and phorone, have been evaluated using TK+/- -3.7.2C mouse lymphoma cells. Mutagenic chemicals induced increases in the number of small colony tk- deficient mutants. This suggested a clastogenic mechanism which was confirmed by demonstrating increases in aberrations and micronucleus frequencies in cultured cells. Vinyl sulfone was found to be the most effective chemical mutagen with induction of genotoxic effects at concentrations as low as 0.25 microgram/ml. The other compounds also produced positive results, but at higher concentrations. Since these compounds are known to deplete glutathione, phorone, a model glutathione depleter, was examined and found to produce similar effects as the other compounds in mouse lymphoma cells. These results suggest that the direct-acting Michael-type reaction has activity relevant to producing a genotoxic effect. Since acrylamide has been found to be a potent germ cell mutagen, this mechanism may be also relevant in the induction of heritable mutagenic risk.
Asunto(s)
Cetonas/toxicidad , Mutágenos/toxicidad , Sulfonas/toxicidad , Acrilatos/metabolismo , Acrilatos/toxicidad , Animales , Biotransformación , Recuento de Células , Linfoma , Ratones , Pruebas de Mutagenicidad/estadística & datos numéricos , Mutágenos/química , Células Tumorales Cultivadas/efectos de los fármacosRESUMEN
2-Amino-6-N-hydroxyadenine (AHA) treated L5178Y/TK (+/-)-3.7.2C mouse lymphoma cells were evaluated for mutations at the tk, hgprt, and Na+/K+ ATPase loci, as well as for gross chromosome aberrations and induction of micronuclei. In addition, AHA was evaluated for its ability to induce HGPRT mutants in CHO cells. AHA was found to induce mutations at all evaluated loci and in both cell types. The TK mutants were primarily large colonies although a few small colonies were also induced, particularly at the higher concentrations. Preliminary cytogenetic analysis of AHA-treated mouse lymphoma cells indicated that some gross aberrations but not micronuclei were induced. The 20 small-colony TK mutants evaluated by banded karyotype indicate that only a small fraction (2 of 20) showed chromosome 11 abnormalities. From these studies, it appears that AHA may be one of a very few chemicals that is capable of inducing multi-locus point mutations, with only slight clastogenic activity. Particularly at the higher concentrations, some of the mutants may contain multi-locus point mutations that result in slow growth.
Asunto(s)
Adenina/análogos & derivados , Mutágenos , Adenina/toxicidad , Animales , Aberraciones Cromosómicas , Trastornos de los Cromosomas , Cricetinae , Cricetulus , Resistencia a Medicamentos , Ratones , Pruebas de Micronúcleos , Mutagénesis , Ouabaína/toxicidad , ATPasa Intercambiadora de Sodio-Potasio/genética , Tioguanina/toxicidad , Células Tumorales CultivadasRESUMEN
The present study was designed to determine and compare the clastogenicity of m-AMSA and camptothecin (CAMP) in vivo in mouse bone marrow and peripheral blood lymphocytes (PBLs), and in vitro in mouse lymphoma L5178Y cells. m-AMSA interferes with topoisomerase II to induce double-strand DNA breaks. CAMP interferes with topoisomerase I to induce single-strand DNA breaks. Thus, we expected the two drugs to induce different types of chromosomal aberrations (CAs). However, both drugs produced quantitatively and qualitatively similar numbers and types of aberrations under similar experimental conditions. In mouse bone marrow exposed over and 18-h period, both drugs (3 mg/kg) induced approximately 30 damaged cells, with an average of 0.4 chromatid breaks per cell (in 100 cells analyzed/mouse). In addition, both drugs induced only chromatid-type aberrations in mouse bone marrow in vivo when exposure occurred during G2. Cell cycle specificity was indicated by the absence of CAs when exposure to the drugs occurred in vivo in mouse PBLs during G0. In L5178Y cells, m-AMSA was considerably more potent for the induction of mutations and somewhat more potent for the induction of CAs than CAMP was. In contrast to the in vivo bone marrow results, the drugs induced high levels of both chromatid- and chromosome-type aberrations in vitro. The ultimate types of chromosomal damage induced by m-AMSA and CAMP result from a complex interaction of (i) cell cycle specific variations in topoisomerase enzyme levels, (ii) the abilities of these drugs to interfere with the orderly DNA breakage/reunion associated with topoisomerase activity, and (iii) the processing of the damage resulting from these interactions.