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Archives of Toxicology (v.75, #10)
No Title by Hsien-Wen Kuo; Tsuen-Ying Hsiao; Jim-Shoung Lai (pp. 569-573).
Exposure to lead has been shown to have a deleterious effect on the immune system. However, the findings of previous studies have been inconsistent. This may have been due to the increased susceptibility to intracellular pathogens and increased polyclonal and antigen-specific responses on exposure to lead. The objective of the current study was to evaluate the immune function of long-term workers with lead in a battery manufacturing plant. Junior high school teachers were used as a control group. Our results showed that the percentage of monocytes was significantly higher among lead workers than in the control group, but T8 cell levels were lower. The T4/T8 ratio was significantly higher among lead workers (1.42) than in the control group (1.18). After adjustment for age, gender and disease using multiple linear regression models, the percentage of B-cells and number of lymphocytes, monocytes and granulocytes were all significantly decreased among lead workers compared with the control group. Our findings showed that lead caused a marked immunotoxic and immunosuppressive effect among long-term lead workers.
Keywords: Lead Occupational exposure Immune system Immunotoxicity Lymphocytes
No Title by Michael M. Iba; Anima Ghosal; Robert Snyder (pp. 574-582).
Lactating adult female mice treated with a single dose of 880 mg/kg i.p. [14C]benzene, and their 2-day-old sucklings similarly treated or nursed by their treated dams were compared in terms of their ability to metabolize benzene to urinary products or reactive intermediates as assessed by covalently-bound benzene derivatives in whole blood or liver DNA. Six metabolite fractions were identified in the urine of sucklings by high performance liquid chromatographic (HPLC) analysis at 5 h following intraperitoneal (direct) treatment with benzene. Three of the metabolite fractions co-chromatographed with authentic phenol, phenyl glucuronide, and muconic acid, and contributed 11, 6.9 and 0.6%, respectively, to the total urinary benzene metabolites. Two of the fractions were unidentified. The sixth and most polar fraction consisted of multiple metabolites, 21% of which were conjugates, and accounted for 72% of the total urinary metabolites. A similar metabolite profile was observed in 24-h urine samples from treated dams with the exception that one of the unidentified fractions in the sucklings was absent and levels of the metabolites were quantitatively higher than those observed in sucklings 5 h following their treatment with benzene. Furthermore, 78% of the most polar fraction from the dams consisted of conjugates compared with 21% of that from the sucklings. The metabolite pattern in urine of sucklings nursed by treated dams was qualitatively similar to, but quantitatively different from the pattern in treated dams. Five hours following intraperitoneal treatment with benzene, covalent binding of the compound to DNA (expressed as pmol benzene equivalents/mg DNA) in sucklings was slightly higher in whole blood (1.15±0.07) than in liver (0.77±0.07), whereas in the dam, it was slightly lower in whole blood (0.88±0.48) than in liver (1.63±0.61). Twenty four hours following benzene exposure in sucklings of benzene-treated dams, DNA binding by the compound in whole blood (3.85±1.05) and liver (0.11±0.03) was higher and lower, respectively than the binding observed in benzene-injected sucklings 5 h following the injection. Our results show that excretable as well as reactive metabolites of benzene are formed substantially by the neonatal mouse, and that the extent of bioactivation of the compound is comparable in the adult and the suckling mouse. The results show also that sucklings of benzene-exposed mothers are exposed to substantial levels of the compound and are potentially susceptible to its toxic effects.
Keywords: Benzene Bioactivation DNA adducts Metabolites Mothers Suckling mice
No Title by Sophie Obrecht-Pflumio; Guy Dirheimer (pp. 583-590).
Ochratoxin A (OTA) gives rise to DNA and deoxyguanosine-3'-monophosphate (dGMP) adducts in vitro using mice kidney microsomes in the presence of arachidonic acid. This result points to the involvement of prostaglandin H synthases, which are present at high levels in the kidney, urinary bladder and seminal vesicles, and/or of lipoxygenases in the metabolic activation of OTA to genotoxic compounds. These enzymes have peroxidase activities. Incubation of OTA with DNA in the presence of horseradish peroxidase (HRP) and cumene hydroperoxide at pH 7.4 led to the formation of one major and three minor adducts with a total adduct level of 42 per 109 nucleotides. Incubation with dGMP gave a total adduct level of 159 per 109 nucleotides. In the presence of H2O2 instead of cumene hydroperoxide, a lower level of adducts was obtained, both with DNA and dGMP. The concentrations of HRP and co-substrate used in this paper were higher than those used by other authors who obtained negative results when they sought DNA adducts of OTA in the presence of HRP and H2O2. The main adduct we obtained with DNA incubated with HRP and OTA had the same chromatographic behaviour as that obtained when DNA or dGMP were incubated with OTA, arachidonic acid and mice kidney microsomes. However, the main adduct obtained with dGMP incubated with HRP and OTA behaved differently. These results show that OTA can be metabolized by a peroxidase to metabolically activated species that bind covalently to DNA and dGMP; however, the main adduct obtained in vitro with HRP and dGMP cannot serve as a model for one of the adducts formed by OTA with DNA because it behaves differently in two chromatographic systems.
Keywords: Ochratoxin A DNA Adducts dGMP adducts Horseradish peroxidase Kidney microsomes Prostaglandin H synthase Cumene hydroperoxide
No Title by Y. Sakamoto; H. Mikuriya; K. Tayama; H. Takahashi; A. Nagasawa; N. Yano; K. Yuzawa; A. Ogata; N. Aoki (pp. 591-596).
The effects of green tea extract catechins on the rat thyroid were examined in a 13-week feeding study and subsequent 2-,4- and 8-week studies. Commercially available polyphenon-60 (P-60) which contains green tea extract catechins at 66.2% was used as a source of catechins. A basic diet containing different concentrations of P-60 was used for experiments. In the 13-week study, 10 rats of each sex were administered diets containing P-60 at 0 (control), 0.625, 1.25, 2.5 and 5.0%. Goiters were observed in the 13-week test. The mean thyroid weight of rats fed a diet containing 5.0% of P-60 (5.0% group) significantly increased to 444% of the control in males and to 304% of the control in females. Histological examinations of the thyroid of the 5.0% group revealed marked hypertrophy and/or hyperplasia of the follicles, some with depletion of colloid and some with rich colloid, and formation of a fibrous capsule. Slight hypertrophy of follicular cells was observed in male rats fed a diet containing 1.25% of P-60 (1.25% group) and female rats fed a diet containing 2.5% of P-60 (2.5% group). Degree and incidence of thyroid lesions were higher in males than in females in the 1.25, 2.5 and 5.0% groups. In the 2–8-week studies, five rats of each sex were given diets containing 0 (control) and 5.0% of P-60. In the 5.0% group, the mean thyroid weight in males significantly increased to 161% of the control as early as 2 weeks and increased to 357% of the control at 8 weeks. Histologically, these goiters were also associated with follicular cell hypertrophy/hyperplasia as in the 13-week study. The degree and incidence of thyroid lesions were higher in males than in females. These results indicate that dietary administration of the green tea extract catechins at high doses induced goiters in rats, and this may be due to antithyroid effects of catechins. In the 13-week study, the no-observed effect level (NOEL) of green tea extract catechins for F344 rats based on histological changes of the thyroid was considered to be 0.625% in males and 1.25% in females in the diet, respectively.
Keywords: Green tea extract catechins Dietary administration Thyroid gland rat Goiter
No Title by Krister Halldin; Cecilia Berg; Åke Bergman; Ingvar Brandt; Björn Brunström (pp. 597-603).
In a previous study, we showed that bisphenol A (BPA) had oestrogen-like effects in bird embryos, causing malformations of the oviducts in Japanese quail (Coturnix japonica) and feminisation of the left testis in chicken (Gallus domesticus). In this study, uptake and distribution of BPA and tetrabromobisphenol A (TBBPA) in embryos and laying quail were examined as well as variables related to reproduction in adult quail following administration of the compounds into the yolk of embryonated eggs. The uptake of radiolabelled BPA, TBBPA and the reference compound diethylstilboestrol (DES) was studied in the embryos using ß-spectrometry. Autoradiography was employed to examine distribution in egg and embryo after yolk sac injection of BPA or TBBPA and in laying birds, following intravenous and oral administration. Following embryonic exposure to BPA or TBBPA, sexually mature male birds were examined for reproductive behaviour and testis morphology, and females were examined for egg laying and oviduct morphology. Neither BPA (200 µg/g egg) nor TBBPA (15 µg/g egg) caused any significant oestrogen-like effects on the variables studied, although effects on the female oviducts after BPA exposure were indicated. Embryonic exposure to DES is known to cause profound effects on male sexual behaviour and female oviduct morphology at doses 3–5 orders of magnitude lower than the BPA and TBBPA doses used in the present study. The proportions of BPA and TBBPA taken up by the embryos after yolk sac injection were similar to the proportion of DES taken up. Differences in bioavailability, therefore do not account for any major part of the potency differences between DES and the two bisphenol A compounds. The concentration of radioactivity in the embryo, as revealed by autoradiography, was low compared with that in the yolk at all stages studied (days 6, 10 and 15). Pronounced labelling of the bile and the allantoic fluid was observed, however, indicating that both compounds were readily metabolised and excreted. Radiolabelled BPA and TBBPA administered to laying quail were largely excreted via the bile and 9 days after oral dosing, only small amounts of the labelled compound remained within the body. Maternal transfer of labelled BPA and TBBPA to the egg was low.
Keywords: Bisphenol A Distribution Endocrine disruption Japanese quail Tetrabromobisphenol A
No Title by T. Gebel; M. Müller; G. Westphal; E. Hallier (pp. 604-608).
Dicyclohexylamine×nitrite is used in chemical formulations as an anti-corrosion agent. N-Nitrosodicyclohexylamine (N-NO-DCHA) can be formed by nitrosation from dicyclohexylamine during the application of these formulations. As most of the nitrosamines are genotoxic carcinogens, the genotoxic potential of N-NO-DCHA was investigated in V79 Chinese hamster cells in the single cell gel assay and the sister chromatid exchange (SCE) test. In addition, N-NO-DCHA cytotoxicity was determined in the neutral red assay. Neutral red uptake was suppressed up to 50% after 24 h incubation at a concentration of ~135 µM. In the single cell gel assay, a significantly elevated and dose-dependent induction of DNA lesions was detected in a concentration range from 5 µM to 100 µM (P<0.001). The use of proteinase K (1 mg/ml) in the lysing solution did not influence these results. In the SCE analysis, a significant induction of SCE was found at a minimum concentration of 5 µM N-NO-DCHA as well. A dose-dependent SCE induction could be detected up to the maximum concentration tested in the assay (100 µM). In conclusion, N-NO-DCHA is genotoxic in V79 cells in the single cell gel assay and the SCE test. With respect to human health hazard prevention, a substitution of dicyclohexylamine×nitrite in chemical formulations used to prevent corrosion is recommended.
Keywords: N-nitrosodicyclohexylamine Comet assay SCE test Neutral red assay V79 cells
No Title by Konstantin Grancharov; Heike Engelberg; Zlatina Naydenova; Gunther Müller; Albert W. Rettenmeier; Evgeny Golovinsky (pp. 609-612).
Eight toxic compounds of natural origin present in the human diet or used as drugs were tested as inhibitors of UDP-glucuronosyltransferase (UGT) activity in rat liver microsomes with 1-naphthol (1-NA), phenolphthalein (PPh) and 4-nitrophenol (4-NP) as substrates. Strong inhibitory effects were observed with tannic acid (tannin) and the antifungal drug griseofulvin (GF): at a concentration of 1 mM, the two compounds completely suppressed the glucuronidation of 1-NA and PPh, respectively. A concentration of 0.1 mM still proved to be highly inhibitory, and even at a concentration as low as 50 µM, tannin produced nearly 50% inhibition of 1-NA conjugation. The UGT isoforms converting 4-NP were less sensitive to the tested compounds (with the exception of GF). Kinetic studies with tannin revealed an uncompetitive type of inhibition toward 1-NA, with an apparent Ki value of 20 µM. The inhibition by GF was non-competitive with respect to PPh and was of a mixed type toward UDP-glucuronic acid, with apparent Ki values of 40 µM and 30 µM, respectively. Tannin and GF did not act as substrates for rat microsomal UGT.
Keywords: UDP-glucuronosyltransferases Natural toxicants Inhibition Tannin Griseofulvin Liver microsomes
No Title by Mariitta Laaksonen; Jorma Mäki-Paakkanen; Hannu Komulainen (pp. 613-617).
3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) is a mutagenic by-product found in chlorinated drinking water. It is a multi-site carcinogen in Wistar rats although the mechanisms of action of the carcinogenesis remain unresolved. We evaluated the ability of MX to promote development of transformation foci in a two-stage cell transformation assay in vitro. C3H 10T1/2 mouse embryonic fibroblasts were exposed to 3-methylcholanthrene (MC, 5 µg/ml) in the initiation phase and to MX (0.5, 1 or 2 µg/ml) or the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA, the positive control, 0.3 µg/ml) during the promotion phase of the assay on dishes. In other experiments, the cells were exposed to MX (0.5, 5 or 10 µg/ml) only in the initiation phase. At the end of the assay (6 weeks from the start of the assay), the transformation foci were counted and scored after fixation and staining of the cells. MC increased the total number of transformation foci per dish and the number of malignant type III foci, and TPA further promoted this phenomenon. When MX was added during the promotion phase in the MC-initiated cells, it promoted the development of the transformation foci in a dose-dependent manner. MX alone (added as an initiator) also slightly increased the development of the foci, including the malignant forms (type II and III), but the effect was not dose-dependent. In contrast to MC-induced foci, TPA did not promote the development of MX-initiated foci, it even decreased their number. The results suggest that MX may also have potential to promote tumor development.
Keywords: Tumor promotion Chlorinated drinking water 3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone MX Cell transformation assay
No Title by Abraham Nyska; Cindy R. Moomaw; Liat Lomnitski; Po Chan (pp. 618-624).
2,4-Hexadienal (2,4-Hx), an unsaturated aldehyde formed by in vivo and in vitro peroxidation of unsaturated lipid induced, in National Toxicology Program (NTP) gavage studies of F344 rats, forestomach hyperplasia in 13-week and 2-year exposures and squamous papilloma and carcinoma in 2-year studies. Hyperplasia was characterized by thickening of all layers of epithelium with particularly prominent proliferation of the basal cells. The present investigation describes the nature and potential significance of glutathione-S-transferase-Pi (GST-Pi) immunoexpression of normal forestomach epithelium, compared to that of 2,4-Hx-related basal cell hyperplasia and squamous cell papilloma and carcinoma. Paraffin-embedded forestomachs from these NTP studies were used to investigate possible correlations between the carcinogenic process and expression of GST-Pi, a physiological metabolic barrier and an inducible phase II detoxifying enzyme suggested to decrease the responsiveness of reactive oxygen species (ROS) and organic electrophilic compounds. The amount of immunopositive staining was graded on a scale of 0 (no staining) to 4 (marked staining). The simple basal epithelium of control rats showed strong immunopositivity. In cases of basal cell hyperplasia from the 13-week and 2-year studies, these cells usually expressed strong immunopositivity for GST-Pi (grade 3 to 4). In the 2-year treated animals only, occasional focal reduction (grade 0 to 2) in immunoreactivity for GST-Pi was noted. In papillomas and squamous cell carcinomas, a wide range of GST-Pi expression was observed, perhaps indicating irregularities in its induction or change in the phenotype of these cells compared to normal or hyperplastic ones. Reduced expression of GST-Pi by the foci of basal cell hyperplasia and in tumor cells may suggest changes in cellular protection from oxidative or electrophilic DNA damage; these changes may result in genetic alterations and be the precursor to clonal expansion.
Keywords: Basal cell hyperplasia F344 rat Glutathione-S-transferase-Pi 2,4-Hexadienal Stomach