Plant studies have been carried out to identify the nature and extent of the formation of adducts with DNA bases when treated with pesticide formulations. DNA extracted from crop plants after treatment with pesticide formulations has yielded evidence of adduct formation. The extent of DNA modification has been established by (32)P postlabeling studies. The radiochromatograms from (32)P postlabeling of isolated plant DNA from grapes, bush beans, soybeans, pumpkins, and cucumbers show elevated adduct levels in treated vegetable plants as compared with untreated controls. A number of different adduct spots appear, likely indicating adduct formation with pesticide molecules or their metabolites. The DNA adducts from hexenal and 4-hydroxy-2-nonenal were clearly observed, indicating oxidative stress and lipid peroxidation in the plant.

Six monofunctional alkylating methanesulphonates of widely varying structures were investigated in the in vitro micronucleus assay with Syrian hamster embryo fibroblast cells. The results were compared with the alkylating activities measured in the 4-(nitrobenzyl)pyridine test (NBP-test) and the N-methyl mercaptoimidazole (MMI-test) as measures for S(N)2 reactivity as well as in the triflouoroacetic acid (TFA) solvolysis and the hydrolysis reaction as measures for S(N)1 reactivity in order to provide insights into the role of alkylation mechanisms on induction of micronuclei. Moreover we compared the results of micronucleus assay with those of the Ames tests in strain TA 100 and TA1535 and with those of the SOS chromotest with the strains PQ37, PQ243, PM21 and GC 4798. The potency of methanesulphonates to induce micronuclei depended only to a certain degree, on the total alkylating activity (S(N)1 and S(N)2 reactivity). An inverse, significant correlation between the Ames test and the micronucleus assay was observed and an inverse correlation between the micronucleus assay and the SOS chromotest with the different strains. The results indicate that the primary mechanism leading to induction of micronuclei is not O-alkylation in DNA as it is the case in the Ames test with the hisG46 strains TA1535 and TA100 and not N-alkylation as with the SOS chromotest. There is evidence that protein alkylation, e.g. in the spindle apparatus in mitosis is decisive for induction of micronuclei by alkylating compounds. The structurally voluminous methanesulphonates 2-phenyl ethyl methanesulphonate and 1-phenyl-2-propyl methanesulphonate show a clear higher micronuclei inducing potency than the other tested though the bulky methanesulphonates possess a lower total alkylating activity than the others. This effect can be explained by a higher disturbance during mitosis after alkylation of the spindle apparatus with the structurally more bulky methanesulphonates.

1,3-Dichloropropene (1,3-DCP) is used as a soil nematocide worldwide. Technical grade 1,3-DCP is genotoxic/mutagenic and carcinogenic. Talcott and King reported that mutagenic activity is lost after purification of 1,3-DCP samples via silica gel column chromatography. We found that mutagenicity and SOS repair in Escherichia coli, strain PM 21, are strongly reduced after purification via silica gel and that mutagenicity and induction of SOS repair depend on oxidative impurities and secondary products. Both isomers (E and Z) of 1,3-DCP are oxidized to 1,3-dichloropropene epoxide (1,3-DCP-Ox). The epoxide is subjected to rapid internal rearrangement to 2,3-dichloropropanal (2,3-DCPA), which spontaneously eliminates HCl and forms the extremely mutagenic, genotoxic, and carcinogenic 2-chloroacrolein (alpha-chloroacrolein) alpha-ClA. Thus, the genotoxic/mutagenic effects of unpurified 1,3-DCP samples mainly depend on alpha-ClA. The underlying genotoxic and mutagenic mechanism is formation of promutagenic exocyclic 1,N(2)-propanodeoxyguanosine adducts of alpha-ClA. Pure 1,3-DCP samples have only a very low S(N)1 reactivity as measured in trifluoroacetic acid solvolysis reactions, hydrolysis, and computed reactivities but possess a moderate S(N)2 reactivity as determined in alkylation tests with the nucleophiles 4-(p-nitrobenzyl)pyridine (NBP) and N-methyl-mercaptoimidazole (MMI). Evidently, the low S(N)1 reactivity is not sufficient to form necessary amounts of O(6)-alkylguanine DNA adducts required for back-mutation in Salmonella typhimurium strain TA1535. The S(N)2 reactivity may, however, lead to other DNA adducts, e.g., N7-guanine adducts, which can induce error prone repair in S. typhimurium strain TA100 and thus lead to back-mutation in this strain. Application of 1,3-DCP samples in agriculture must be considered as a mutagenic risk because the samples can be oxidized and form the extremely mutagenic alpha-ClA. As a consequence, it is questionable whether any stabilizers can prevent oxidation during application.

Both animal and epidemiological studies support an effect of fatty acid composition in the diet on cancer development, in particular on colon cancer. We investigated the modulating effect of supplementation of the diet of female F344 rats with sunflower-, rapeseed-, olive-, or coconut oil on the formation of the promutagenic, exocyclic DNA adducts in the liver, an organ where major metabolism of fatty acids takes place. 1,N6-ethenodeoxyadenosine (etheno-dA), 3,N4-ethenodeoxycytidine (etheno-dC) and 1,N2-propandodeoxyguanosine from 4-hydroxy-2-nonenal (HNE-dGp) were determined as markers for DNA-damage derived from lipid peroxidation products and markers for oxidative stress. 8-Oxo-deoxyguanosine (8-Oxo-dG) was also measured as direct oxidative stress marker. The body weight of the rats was not influenced by the four diets containing the different vegetable oils during the 4-week feeding period.Highest adduct levels of etheno-dC (430±181 adducts/109 parent bases), HNE-dGp (617±96 adducts/109 parent bases) and 8-Oxo-dG (37,400±12,200 adducts/109 parent bases) were seen in rats on sunflower oil diet (highest linoleic acid content). Highest adducts levels of etheno-dA (133±113 adducts/109 parent bases) were found in coconut oil diet (lowest content of linoleic acid). Weakly positive correlations between linoleic acid content in the four diet groups were only observed for levels of HNE-dGp and 8-Oxo-dG. Neither the diet based on olive oil (which contains mainly oleic acid) nor the diet based on rapeseed oil (containing α-linolenic acid) exerted any significant protective effect against oxidative DNA damage. Our results indicate that a high linoleic acid diet may contribute to oxidative stress in the liver of female rats leading to a marginal increase in oxidative DNA-damage.

Ochratoxin A (OTA), a mycotoxin produced by several fungi of Aspergillus and Penicillium species, may contaminate agricultural products, resulting in chronic human exposure. In rats, OTA is a potent nephrotoxin, and repeated administration of OTA for 2 years to rats in doses up to 0.21 mg/kg of body wt resulted in high incidences of renal tumors arising from the proximal tubular epithelial cells. The mechanism of tumor formation by OTA in the kidney is not well-defined, and controversial results regarding mode of action have been published. The aim of this study was to characterize dose-dependent changes induced by OTA by application of clinical chemistry, biochemical markers, and toxicokinetics for a better conclusion on modes of action. Administration of OTA (0, 0.25, 0.5, 1, and 2 mg/kg of body wt) to male F344 rats (n = 3 per group) by oral gavage for 2 weeks resulted in a dose-dependent increase in OTA plasma concentrations and concentrations of OTA in both liver and kidney. Although oxidative stress has been implicated in OTA carcinogenicity, treatment with OTA did not induce overt lipid peroxidation or an increase in 8-oxo-7,8-dihydro-2'deoxyguanosine (8-OH-dG) in kidney. In the kidney, OTA-induced pathology was present at all dose levels administered, with a clear increase in severity related to dose. Pathology was restricted to the outer stripe of the outer medulla and consisted of disorganization of the tubule arrangement, frequent apoptotic cells, and abnormally enlarged nuclei scattered through the S3 tubules. Consistent with the histopathology, a dose-dependent increase in the expression of proliferating cell nuclear antigen (PCNA), indicative of cell proliferation, was observed in kidneys, but not in livers of treated animals. The most prominent change in the composition of urine induced by OTA analyzed by 1H NMR and principal component analysis consisted of a major increase in the excretion of trimethylamine N-oxide. However, typical changes observed with other proximal tubular toxins such as increased excretion of glucose were not observed at any of the doses administered. Similarly, treatment with OTA had no clear effects on clinical chemical parameters indicative of nephrotoxicity, although urinary volume was increased at the higher-dose groups. Taken together, the uncommon changes induced by OTA suggest that a unique mechanism may be involved in OTA nephrotoxicity and carcinogenicity.