Influence of chronic ethanol uptake and acute acetaldehyde treatment on the chromosomes of bone-marrow cells and peripheral lymphocytes of Chinese hamsters

Acetaldehyde as a Food Flavoring Substance: Aspects of Risk Assessment

The Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) has reviewed the currently available data in order to assess the health risks associated with the use of acetaldehyde as a flavoring substance in foods. Acetaldehyde is genotoxic in vitro. Following oral intake of ethanol or inhalation exposure to acetaldehyde, systemic genotoxic effects of acetaldehyde in vivo cannot be ruled out (induction of DNA adducts and micronuclei). At present, the key question of whether acetaldehyde is genotoxic and mutagenic in vivo after oral exposure cannot be answered conclusively. There is also insufficient data on human exposure. Consequently, it is currently not possible to reliably assess the health risk associated with the use of acetaldehyde as a flavoring substance. However, considering the genotoxic potential of acetaldehyde as well as numerous data gaps that need to be filled to allow a comprehensive risk assessment, the SKLM considers that the use of acetaldehyde as a flavoring may pose a safety concern. For reasons of precautionary consumer protection, the SKLM recommends that the scientific base for approval of the intentional addition of acetaldehyde to foods as a flavoring substance should be reassessed.

Stellungnahme zu Acetaldehyd als Aromastoff: Aspekte der Risikobewertung

Opinion on acetaldehyde as a flavouring substance: considerations for risk assessment

Acetaldehyde occurs naturally in many foods and is also used as a flavouring due to its fruity aroma. The International Agency for Research on Cancer (IARC) classified acetaldehyde as possibly carcinogenic to humans and, in combination with oral intake via alcoholic beverages, as carcinogenic to humans. Therefore, the question arises whether the use of acetaldehyde as a flavouring agent is still justifiable. The Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) reviewed the scientific basis for health risk assessment of the use of acetaldehyde as a flavouring substance and adopted an opinion. Based on the available data, it is at present not possible to conclude if acetaldehyde is genotoxic and mutagenic in vivo after oral exposure. There is also uncertainty regarding the contribution of acetaldehyde as a flavouring substance to the overall exposure to acetaldehyde. Therefore, a science-based assessment on health risk related to the use of acetaldehyde as a flavouring is not possible at present. Considering the genotoxic potential as well as numerous data gaps that need to be closed for a full risk assessment, the SKLM is concerned about the safety of acetaldehyde as a flavouring substance. For reasons of precautionary consumer protection, the SKLM considers that the use of acetaldehyde as a food additive should be re-evaluated.

Lack of micronucleus induction activity of ethyl tertiary-butyl ether in the bone marrow of F344 rats by sub-chronic drinking-water treatment, inhalation exposure, or acute intraperitoneal injection

Ethyl tertiary-butyl ether (ETBE) is an oxygenated gasoline additive synthesized from ethanol and isobutene that is used to reduce CO2 emissions. To support the Kyoto Protocol, the production of ETBE has undergone a marked increase. Previous reports have indicated that exposure to ETBE or methyl tertiary-butyl ether resulted in liver and kidney tumors in rats and/or mice. These reports raise concern about the effects of human exposure being brought about by the increased use of ETBE. The present study was conducted to evaluate the genotoxicity of ETBE using micronucleus induction of polychromatic erythrocytes in the bone marrow of male and female rats treated with ETBE in the drinking-water at concentrations of 0, 1,600, 4,000 or 10,000 ppm or exposed to ETBE vapor at 0, 500, 1,500 or 5,000 ppm for 13 weeks. There were no significant increases in micronucleus induction in either the drinking water-administered or inhalation-administered groups at any concentration of ETBE; although, in both groups red blood cells and hemoglobin concentration were slightly reduced in the peripheral blood in rats administered the highest concentration of ETBE. In addition, two consecutive daily intraperitoneal injections of ETBE at doses of 0, 250, 500 or 1,000 mg/kg did not increase the frequency of micronucleated bone marrow cells in either sex; all rats receiving intraperitoneal injections of ETBE at a dose of 2,000 mg/kg died after treatment day 1. These data suggest that ETBE is not genotoxic in vivo.

Effect of gene polymorphisms and ethanol consumption on micronucleus frequency in human reticulocytes: a preliminary study

OBJECTIVE

Results from previous studies suggest that alcohol consumption can be genotoxic on peripheral lymphocytes. The aim of our study was to examine the association of alcohol consumption and its genotoxic effect on hematopoietic stem cells in vivo.

METHODS

We investigated 156 healthy Japanese males in a cross-sectional study. Lifestyles, including alcohol drinking behavior and cigarette smoking status, were investigated by means of a self-completed questionnaire. Polymorphisms of ADH1B and ALDH2 were identified by PCR-restriction fragment length polymorphism (RFLP) analysis. The presence of micronuclei in transferrin-positive reticulocytes (MN-RET) was detected with a single-laser flow cytometer. Associations between the genetic polymorphisms, lifestyle factors, and MN-RET frequency were statistically analyzed.

RESULTS

We found a significant difference in the mean frequencies of MN-RET between habitual drinkers and non-habitual drinkers (P = 0.043), and between the ALDH2*1/*1 and ALDH2*2/*2 genotype (P = 0.015). The ADH1B*2 and ALDH2*2 haplotype was estimated to have a significantly higher influence on MN-RET frequency than the ADH1B*2 and ALDH2*1 haplotype (P = 0.00035), and the frequency of alcohol consumption played a significant role in MN-RET frequency on the background of the ADH1B*2 and ALDH2*1 haplotype (P = 0.012).

CONCLUSION

The results of our study suggest a possible association between the ADH1B and ALDH2 polymorphism and the genotoxic effects of alcohol drinking on hematopoietic stem cells.

Nucleolar organizer regions (AgNOR) and subepithelial vascularization as field cancerization markers in oral mucosa biopsies of alcoholic and smoking patients

OBJECTIVE

The aim of this study was to show that variations in nucleolar organizer regions (AgNOR) and the increase in subepithelial vascularization could reveal changes related to markers of field cancerization in alcoholic and smoking patients who have not yet expressed clinical or histological malignant lesions.

STUDY DESIGN

Quantitative variations in epithelial AgNOR and in the vascularization of the underlying connective tissue were assessed by image analysis in histologically normal biopsy specimens from alcohol drinkers and smoking patients (DS). AgNORs were evidenced by silver staining and vessel walls were labeled by immunohistochemical demonstration of the CD34 antigen. Samples of oral mucosa of nonalcoholic, nonsmoking patients (NDS) obtained during surgical procedures served as controls. Eight parameters related to number, volume, and shape of nuclei and AgNORs, and 4 parameters related to number and diameter of vascular sections were evaluated. Differences between DS and NDS groups were statistically evaluated by means of ANOVA test and posterior Bonferroni comparisons.

RESULTS

The morphometric analysis revealed more irregular-shaped AgNORs in the superficial and suprabasal layers of the oral mucosa of DS patients. The suprabasal layers also exhibited a significantly larger number of AgNORs. The normal oral mucosa of DS patients exhibited a greater vascular density, with predominance of small-caliber blood vessels underlying the basement membrane.

CONCLUSION

The variations in AgNOR and epithelial vascularization would be practical biomarkers to evaluate changes underlying the augmented risk of cancerization in oral mucosa.

Prospective Study of Alcohol Consumption and Risk of Oral Premalignant Lesions in Men

Recent case-control studies indicate that alcohol increases the risk of oral premalignant lesions (OPL) among tobacco users, but the independent association between alcohol and OPL remains unclear. We prospectively evaluated the association between alcohol consumption and the incidence of OPL. Participants were 41,458 men in the Health Professionals Follow-up Study. Alcohol consumption was assessed every 4 years using validated food frequency questionnaires. We confirmed clinically or histopathologically diagnosed OPL events occurring between 1986 and 2002 by medical record review (193 cases). Multivariate-adjusted relative risks of OPL were calculated from Cox proportional hazards models. With detailed control for tobacco and other variables, multivariate relative risks (95% confidence intervals) were 1.7 (0.9-3.2) for drinkers of 0.1 to 14.9 g/d, 2.9 (1.5-5.6) for 15 to 29.9 g/d, and 2.5 (1.3-5.1) for > or =30 g/d, compared with nondrinkers. Approximately one additional drink per day (12.5 g) was associated with a 22% increase in risk (P < 0.001). The associations did not vary by beverage type, frequency, or consumption with meals. Results were similar when restricted to cases of oral epithelial dysplasia. Alcohol increased OPL risk in never-users of tobacco as well as in past or current users. An interaction between alcohol and tobacco was apparent by their more-than-additive joint effects. Alcohol is an independent risk factor for OPL, regardless of beverage type or drinking pattern. Recommendations to reduce alcohol intake have the potential to reduce incidence of OPL in nonsmokers and smokers alike.

Epigenetic inactivation of theSFRP genes is associated with drinking, smoking and HPV in head and neck squamous cell carcinoma

The soluble frizzled receptor protein (SFRP) family encodes antagonists of the WNT pathway, and silencing of these genes, through promoter hypermethylation, leads to constitutive WNT signaling. In bladder cancers, hypermethylation of the SFRP genes occurs more often in current and former smokers and is a strong predictor of poor patient survival. Hence, we examined methylation of these genes in another tobacco-related epithelial cancer, head and neck squamous cell carcinoma (HNSCC), to determine if the pattern of tobacco exposure again predicts the epigenetic alteration of these genes. Using methylation-specific PCR, the prevalence of methylation of SFRP1, SFRP2, SFRP4 and SFRP5 was 35, 32, 35 and 29%, respectively among 350 HNSCC cases. Promoter methylation of SFRP1 occurred more often in both heavy (OR 3.5, 95% CI 0.9-13.7) and light drinkers (OR 3.7, 95% CI 1.0-14.3) compared to nondrinkers. SFRP4 promoter methylation, on the other hand, occurred at a higher prevalence in never smokers and former smokers than in current smokers, and also was independently associated with HPV16 viral DNA. A joint effects model of SFRP4 promoter methylation demonstrated that smoking status and HPV virus significantly interacted (p < 0.04) such that never smokers with HPV16 had an OR of SFRP4 methylation of 9.0 (95% CI 2.1-38.6). These results suggest that epigenetic alterations of the SFRP genes are highly prevalent in HNSCC, and that the clonal selection for these alterations is complex and may be related to the carcinogenic exposures that are known risk factors for this disease.

Effects of chlorophyllin on acetaldehyde: lack of modulation of the rate of sister-chromatid exchanges in mouse bone marrow, and of complex formation in aqueous solution

Acetaldehyde (Ace) is a reactive compound widely found in natural and industrialized products. On the other hand, chlorophyllin (Chl) is a chloropyll derivative which has shown DNA modulatory effects in several models. The first aim of the present study was to determine the capacity of Ace to increase the rate of sister-chromatid exchanges (SCEs) in mouse bone marrow cells in vivo, as well as to determine its capacity to modify the mitotic index (MI) and the average generation time (AGT). For this experiment we tested four dosages of Ace by the i.p. route (0.4, 4.0, 40.0 and 400 mg/kg), and found a genotoxic effect with the two highest dosages (more than double the basal level was observed with 400 mg/kg). We also found that none of the doses tested modified the MI or the AGT. A second objective was to explore the potential of Chl to modulate the genotoxicity of Ace in the same model. We evaluated whether an oral administration of Chl (2.0, 6.0 and 10.0 mg/kg), given 1 h before an i.p. administration of Ace (100 mg/kg), could modulate the SCEs produced by the mutagen. The result showed a similar SCE rate in both, the Ace-treated mice and those administered with the two chemicals, indicating that Chl was not a modulatory chemical on the genotoxicity of Ace. No modifications were observed concerning the MI or the AGT either. A third objective was to determine whether the two compounds (Ace and Chl) may form a molecular complex in aqueous solution. In agreement with the lack of modulatory effect by Chl, a reversed HPLC and a spectrophotometric analysis showed that the two compounds were unable to form a complex. This report confirms the importance of the specificity concerning the interaction mutagen/antimutagen.

Effect of disulfiram on the genotoxic potential of acetaldehyde in mouse spermatogonial cells

The initial purpose of the study was to determine the potential of acetaldehyde (Ace) to increase the rate of sister-chromatid exchanges (SCEs) in mouse spermatogonia. We tested four doses of Ace (from 0.4 to 400.0 mg/kg), including a negative and a positive control group (distilled water and cyclophosphamide, respectively). The results showed that all tested doses were SCE inducers. The highest tested dose increased the control level more than three times. Also, the cumulative frequencies of SCEs per cell were higher in the Ace-treated animals than in the control cells. Ace is transformed into acetate through the enzyme aldehyde dehydrogenase, a process that may be blocked by disulfiram (Dis) generating the accumulation of Ace. The second purpose of the study was to determine if the administration of Dis (150 mg/kg) could increase the SCE rate produced by non-genotoxic doses of Ace. (0.004 and 0.04 mg/kg). The animals treated with the two doses of Ace alone showed no increase in the frequency of SCEs; also, Dis by itself was not an SCE inducer. However, the groups of animals previously treated with Dis showed an increase of 31 and 60% with respect to the values obtained with the two doses of Ace alone. Furthermore, the cumulative frequencies of SCEs per cell were higher in the animals administered with both compounds together than in those treated with them separately. These results suggest the need to extend this type of study to other models.

Sister-chromatid exchanges induced by disulfiram in bone marrow and spermatogonial cells of mice treated in vivo

Disulfiram is a widely used drug to treat alcoholism due to its capacity to inhibit the metabolism of acetaldehyde; however, its genotoxic potential is not well known. Thus, the aim of this investigation was to determine whether the chemical may induce sister-chromatid exchanges (SCEs) in an in vivo study using mouse bone marrow and spermatogonial cells. We used doses of 200, 400 and 800 mg/kg body weight and compared the obtained data with the values determined in a negative control group as well as with a positive control group (cyclophosphamide, 50 mg/kg). The results in both systems indicated a weak genotoxic response by the chemical. In the case of bone marrow, a significant SCE level was achieved only with the high tested dose, but in spermatogonial cells the three doses tested showed a significant difference with respect to the negative control. No significant alterations in the mitotic index or in the cell proliferation kinetics were observed in somatic cells. Concerning the effect of cyclophosphamide, an increase in the level of SCEs was observed in both types of cells, reaching more than three times the values obtained in their respective control groups.

Possible mechanisms by which alcohol may influence the development of oral cancer--a review

Although pure ethanol has never been shown to be carcinogenic in laboratory experiments, alcoholic beverages are now recognised as being important aetiological factors in the development of oral cancer. Despite this, the exact mechanism by which alcohol may exert an influence upon the oral mucosa has received less attention. An overview of the association of alcohol and oral cancer, both in combination with tobacco and without, is provided and consideration given to some of the pathways by which alcohol exerts its effect upon the oral mucosa.

Specific tandem GG to TT base substitutions induced by acetaldehyde are due to intra-strand crosslinks between adjacent guanine bases

Acetaldehyde is present in tobacco smoke and automotive exhaust gases, is produced by the oxidation of ethanol, and causes respiratory organ cancers in animals. We show both the types and spectra of acetaldehyde-induced mutations in supF genes in double- and single-stranded shuttle vector plasmids replicated in human cells. Of the 101 mutants obtained from the double-stranded plasmids, 63% had tandem base substitutions, of which the predominant type is GG to TT transversions. Of the 44 mutants obtained from the single-stranded plasmids, 39% had tandem mutations that are of a different type than the double-stranded ones. The GG to TT tandem substitutions could arise from intra-strand crosslinks. Our data indicate that acetaldehyde forms intra- as well as inter-strand crosslinks between adjacent two-guanine bases. Based upon the following observations: XP-A protein binds to acetaldehyde-treated DNA, DNA excision repair-deficient xeroderma pigmentosum (XP) cells were more sensitive to acetaldehyde than the repair-proficient normal cells, and a higher frequency of acetaldehyde-induced mutations of the shuttle vectors was found in XP cells than in normal cells, we propose that the DNA damage caused by acetaldehyde is removed by the nucleotide excision repair pathway. Since treatment with acetaldehyde yields very specific GG to TT tandem base substitutions in DNA, such changes can be used as a probe to identify acetaldehyde as the causal agent in human tumors.

Acetaldehyde: genotoxicity and cytotoxicity in human lymphocytes

We evaluated the DNA damaging effects of ethanol and its major metabolite, acetaldehyde. Freshly isolated human lymphocytes from two healthy donors were incubated with 0, 1.56, 6.25, 25, and 100 mM of ethanol or acetaldehyde in complete medium for 1 h. We used a newly developed, sensitive, alkaline microgel electrophoresis technique to quantitate single- and double-strand DNA breaks or alkali-labile sites in individual cells. Ethanol did not induce DNA strand breaks. However, acetaldehyde induced both single-strand (even at the lowest concentration of 1.56 mM) and double-strand breaks (only at the highest concentration of 100 mM). Following exposure to acetaldehyde, cells were incubated in complete medium for 30, 60, and 120 min. During this incubation period, most cells were unable to repair DNA single- and double-strand breaks caused by acetaldehyde. We also observed a significant cell loss after exposure to acetaldehyde. To our knowledge, this is the first study demonstrating DNA single- and double-strand breaks by acetaldehyde.

Sister-chromatid exchange: second report of the Gene-Tox Program

This paper reviews the ability of a number of chemicals to induce sister-chromatid exchanges (SCEs). The SCE data for animal cells in vivo and in vitro, and human cells in vitro are presented in 6 tables according to their relative effectiveness. A seventh table summarizes what is known about the effects of specific chemicals on SCEs for humans exposed in vivo. The data support the concept that SCEs provide a useful indication of exposure, although the mechanism and biological significance of SCE formation still remain to be elucidated.

Acetaldehyde activation of poly(ADP-ribose)polymerase in hepatocytes of mice treated in vivo

The activities of poly(ADP-ribose) polymerase and of DNA polymerases alpha and beta and the level of cytochrome P450 were determined in mouse parenchymal liver cells 5 h after treatment with 0.1, 0.3, 1.0, and 3.0 mumole of acetaldehyde. Injection with 1.0 and 3.0 mumole of acetaldehyde induced an increase in poly(ADP-ribose) polymerase activity and in the P450 level, but had no effect on DNA polymerases. The stimulation of poly(ADP-ribose) polymerase activity can be used as an index of induced DNA damage. The possibility of using this experimental approach with other cells derived from mice treated in vivo with different xenobiotics is discussed.

Effects of vinyl acetate and acetaldehyde on sperm morphology and meiotic micronuclei in mice

The testicular genotoxic effects of vinylacetate (VA) and its hydrolysis product, acetaldehyde (AA), were studied in mice by analyzing the induction of morphologically abnormal sperm and meiotic micronuclei. VA significantly increased the frequency of sperm abnormalities at 500 mg/kg/day while lower doses were ineffective. AA did not induce abnormal sperm. Neither of the compounds influenced the frequency of meiotic micronuclei. VA, but not AA, caused a dose-dependent decrease in sperm production and a reduction of testicular weight at 500 and 125 mg/kg/day.

A mutagenicity assessment of acetaldehyde

Acetaldehyde has been shown in studies by several different laboratories to be a clastogen (chromosome-breaking) and inducer of sister-chromatid exchanges in cultured mammalian cells (Chinese hamster cells and human lymphocytes). Although there have been very few studies in intact mammals, the available evidence suggests that acetaldehyde produces similar cytogenetic effects in vivo. The production of cytogenetic abnormalities may be related to the ability of acetaldehyde to form DNA-DNA and/or DNA-protein cross-links. Acetaldehyde apparently has not been evaluated for its ability to cause gene mutations in cultured mammalian cells, but it has been shown to produce sex-linked recessive lethals in Drosophila. In general, bacteria tests have been negative. Although acetaldehyde is a genotoxic cross-linking agent, it does not appear to cause DNA strand breaks. There were no studies available regarding the potential of acetaldehyde to produce genetic damage in mammalian germ cells in vivo. Most mutagenicity testing on acetaldehyde has been motivated by attempts to define the proximate mutagen in ethanol metabolism.

International Commission for Protection against Environmental Mutagens and Carcinogens. ICPEMC Working Paper No. 15/1. Genetic effects of ethanol

Alcoholics have a higher frequency of chromosomal aberrations and sister-chromatid exchanges (SCEs) in their peripheral lymphocytes. In human and mammalian cells in vitro, ethanol generally does not induce genetic damage, but it induces SCEs in the presence of an exogenous metabolic system. In human lymphocytes in vitro, ethanol induces SCEs in the presence of alcohol dehydrogenase. In animals in vivo, ethanol induces a variety of genetic effects, including SCEs, micronuclei, dominant lethal mutations and aneuploidy in mouse eggs. There is some indication that ethanol may lead to genetic damage in sperm. In bacteria, ethanol is at best marginally active. Ethanol leads to anomalous chromosome segregation in Aspergillus, to mutations in yeast, to chromosomal aberrations and SCEs in plant root tips and to disturbances of meiosis and micronuclei in tetrads in Zea and Tradescantia respectively. The first metabolite of ethanol, acetaldehyde is mutagenic in a variety of test systems. The mutagenic activity of acetaldehyde in bacteria is questionable, but there is no doubt of its mutagenic activity in a variety of eukaryotic test systems in vitro as well as in vivo.

International Commission for Protection against Environmental Mutagens and Carcinogens. ICPEMC Working Paper No. 15/5. Acute aldehyde syndrome and chronic aldehydism

Different types of alcohol dehydrogenase and of aldehyde dehydrogenase lead to different blood acetaldehyde levels. With respect to acetaldehyde levels in human blood 3 types can be distinguished: (1) the normal range, (2) the acute aldehyde syndrome, and (3) the chronic aldehydism. Acetaldehyde is electrophilic and reacts with nucleophilic groups of various macromolecules including DNA. Acetyldehyde inhibits synthetic and metabolic pathways, it interferes with the polymerization of tubulin and stimulates collagen synthesis. By depletion of cellular glutathione levels, acetaldehyde leads to lipid peroxidation and to the formation of malonaldehyde. There are indications that acetaldehyde may play a role in positively reinforcing mood changes induced by alcohol in humans.

Induction of micronuclei by vinyl acetate in mouse bone marrow cells and cultured human lymphocytes

A dose-dependent increase in micronucleated polychromatic erythrocytes was observed in the bone marrow of male C57B1/6 mice 30 h after a single intraperitoneal injection of vinyl acetate (250, 500, 1000 or 2000 mg/kg b.wt.; (9-14 animals per group). The effect was statistically significant at 1000 mg/kg (1.33 +/- 0.29% vs. 0.6 +/- 0.10% in olive oil-treated controls) and at 2000 mg/kg (1.57 +/- 0.19%) of vinyl acetate. These doses were fatal to 6 (1000 mg/kg) and 8 (2000 mg/kg) out of 14 animals in both groups. The ratio of polychromatic to normochromatic cells decreased as a function of vinyl acetate dose. Cyclophosphamide (20 mg/kg), used as a positive control chemical, induced a clear increase in micronucleated polychromatic erythrocytes (2.07 +/- 0.20%). None of the treatments affected the number of micronuclei in normochromatic erythrocytes. In human whole-blood lymphocyte cultures, micronucleus induction by a 48-h treatment with vinyl acetate (0.125, 0.25, 0.5, 1 and 2 mM; 24 h after culture initiation) was studied in lymphocytes with preserved cytoplasm from smear slides prepared by a method involving the removal of erythrocytes at harvest by sodium cyanide treatment to improve preparation quality. The frequency of micronucleated lymphocytes reached a peak at 0.5 mM (3.2 +/- 1.0% vs. 0.9 +/- 0.1% in control cultures) and 1 mM (3.1 +/- 0.7%), with a decline at 2 mM probably because of a toxic effect resulting in mitotic inhibition.

Initiation of in vitro cell transformation by formaldehyde and acetaldehyde as measured by attachment-independent survival of cells in aggregates

The ability of formaldehyde and acetaldehyde to initiate transformation of a rat kidney cell line has been studied using a newly developed two-stage in vitro cell transformation assay. The assay is based on measurements of attachment-independent survival of cells in aggregates. Short treatment with non-cytotoxic doses of formaldehyde and acetaldehyde did not affect survival of the cells in the aggregate assay system. However, when the aldehyde treatment was followed by exposure of the cells to the tumor promoters TPA and PDD, a considerable increase in the number of viable cells was observed. On a molar basis, formaldehyde was about 100 times more potent than acetaldehyde in initiation of cell transformation. The data showed that cells derived from aggregates of cultures treated with formaldehyde or acetaldehyde followed by exposure to TPA possessed a considerably higher ability to form colonies in soft agar than untreated control cells.

Comparison of in vivo and in vitro cytogenetic assay results

In vitro mutagenicity assays have largely replaced whole animal studies for screening compounds for genotoxic potential. While numerous comparisons have been made between the results of these assays and cancer assays in rodents, comparisons between in vitro and in vivo mutagenicity studies where the genetic endpoints are the same have not been published. To this extent, the published literature was reviewed for chemicals that had been tested in both in vitro and in vivo cytogenetic assays. Two hundred sixteen chemicals were identified, and definitive test results were obtained for 181 of them. Results from the two assays agreed on 126 of the compounds and of the 55 compounds for which the results did not agree, 53 were positive in vitro and negative in vivo. The proportion of "false positives" and the significance of the two "false negatives" are discussed.

DNA-damaging activity of biotic and xenobiotic aldehydes in Chinese hamster ovary cells

Alkaline elution was employed to study DNA damage in CHO-Kl cells treated with a series of biotic and xenobiotic aldehydes. DNA cross-linking was measured in terms of the reduction in the effect of methyl methanesulphonate on the kinetics of DNA elution and was observed in cells treated with formaldehyde, acetaldehyde, methylglyoxal and malonaldehyde. Propionaldehyde, valeraldehyde, hexanal and 4-hydroxynonenal produced DNA single-strand breaks, or lesions which were converted to breaks in alkali. Both types of DNA damage occurred in cells exposed to malealdehyde. These findings support the hypothesis of a carcinogenic effect of the aldehydic products (malonaldehyde, methylglyoxal, propionaldehyde, hexanal, 4-hydroxynonenal) released in biomembranes during lipid peroxidation.

Mutagenic, teratogenic and pharmacokinetic properties of cyclophosphamide and some of its deuterated derivatives

To elucidate which metabolic pathway leads to the ultimate mutagenic and teratogenic metabolite of cyclophosphamide (CPA), the mutagenicity in vitro as well as the teratogenicity in vivo and the pharmacokinetics of CPA and several deuterated analogs (5,5-d2-CPA, 4,4-d2-CPA and 4,4-6,6-d4-CPA) were compared. 5,5-d2-CPA was less mutagenic (isotope effects between 1.7 and 12.3 were found for sister-chromatid exchanges and structural chromosomal aberrations in CHO cells and in the Ames test) and less teratogenic (deuterium isotope effect between 2 and 3) than CPA and the other deuterated analogs. Because the concentrations of 5,5-d2-CPA in pregnant mice and their embryos were equal to or even exceeded those of CPA and the other deuterated analogs, a particular metabolic pathway involving a fission of the C-D or C-H bond on the C-5 rather than the parent drug must be responsible for the isotope effect observed. It had previously been shown (Cox et al., 1976) that the 5,5-d2-CPA has a decreased anti-tumor activity in vivo (isotope effect 7-13) which was accompanied by a decreased formation of phosphoramide mustard and acrolein in vitro (isotope effect 5.3). Our results suggest that phosphoramide mustard is an important proximate metabolite of CPA with regard to the mutagenicity and teratogenicity of the drug. These results show for the first time that labeling of drugs with stable isotopes offers a promising approach to the study of the mechanism of the mutagenic and teratogenic actions of drugs.