Baicalein Alleviates Arsenic-induced Oxidative Stress through Activation of the Keap1/Nrf2 Signalling Pathway in Normal Human Liver Cells

BACKGROUND

Oxidative stress is a key mechanism underlying arsenicinduced liver injury, the Kelch-like epichlorohydrin-related protein 1 (Keap1)/nuclear factor E2 related factor 2 (Nrf2) pathway is the main regulatory pathway involved in antioxidant protein and phase II detoxification enzyme expression. The aim of the present study was to investigate the role and mechanism of baicalein in the alleviation of arsenic-induced oxidative stress in normal human liver cells.

METHODS

Normal human liver cells (MIHA cells) were treated with NaAsO2 (0, 5, 10, 20 μM) to observe the effect of different doses of NaAsO2 on MIHA cells. In addition, the cells were treated with DMSO (0.1%), NaAsO2 (20 μM), or a combination of NaAsO2 (20 μM) and Baicalein (25, 50 or 100 μM) for 24 h to observe the antagonistic effect of Baicalein on NaAsO2. Cell viability was determined using a Cell Counting Kit- 8 (CCK-8 kit). The intervention doses of baicalein in subsequent experiments were determined to be 25, 50 and 100μM. The intracellular content of reactive oxygen species (ROS) was assessed using a 2',7'-dichlorodihydrofluorescein diacetate (DCFHDA) probe kit. The malonaldehyde (MDA), Cu-Zn superoxide dismutase (Cu-Zn SOD) and glutathione peroxidase (GSH-Px) activities were determined by a test kit. The expression levels of key genes and proteins were determined by real-time fluorescence quantitative polymerase chain reaction (qPCR) and Western blotting.

RESULTS

Baicalein upregulated the protein expression levels of phosphorylated Nrf2 (p-Nrf2) and nuclear Nrf2, inhibited the downregulation of Nrf2 target genes induced by arsenic, and decreased the production of ROS and MDA. These results demonstrate that baicalein promotes Nrf2 nuclear translocation by upregulating p-Nrf2 and inhibiting the downregulation of Nrf2 target genes in arsenic-treated MIHA cells, thereby enhancing the antioxidant capacity of cells and reducing oxidative stress.

CONCLUSION

Baicalein alleviated arsenic-induced oxidative stress through activation of the Keap1/Nrf2 signalling pathway in normal human liver cells.

Forsythoside B alleviates osteoarthritis through the HMGB1/TLR4/NF-κB and Keap1/Nrf2/HO-1 pathways

Osteoarthritis (OA) is a joint pain and dysfunction syndrome resulting from severe joint degeneration. Inflammation and degeneration of the articular cartilage are two main features of OA and have tight interactions during OA progression. Conventional treatment with nonsteroidal anti-inflammatory drugs has been widely utilized clinically, whereas the side effects have restricted their application. Forsythoside B has been found with anti-inflammatory effects and antiapoptosis in inflammatory diseases, whereas in OA it remains poorly understood. Interleukin (IL)-1β (10 ng/mL) was taken to induce an OA cell model on HC-A chondrocytes and an OA rat model was constructed for in vivo experiments. Forsythoside B was adopted to treat HC-A chondrocytes and OA rats. As shown by the data, Forsythoside B hampered IL-1β-elicited rat chondrocyte apoptosis, oxidative stress, and facilitated proliferation. The profiles of inflammatory factors, NOD-like receptor family pyrin domain containing 3 inflammasomes, Kelch-like epichlorohydrin-associated protein-1 (Keap1), and nuclear factor-κB (NF-κB) phosphorylation were suppressed by Forsythoside B, whereas the nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) levels were promoted. Further, Forsythoside B mitigated cartilage damage and degeneration. Moreover, the oxidative stress and inflammation mediators in the cartilage tissue of OA rats were remarkably abated. Collectively, Forsythoside B hinders the NF-κB and Keap1/Nrf2/HO-1 pathways to curb IL-1β-elicited OA rat oxidative stress and inflammation both in vivo and ex vivo, ameliorating OA development. All over, this study provides an underlying strategy for treating OA, which might help the clinical treatment of OA patients.

[THE CELLULAR COMPOSITION OF THE EPITHELIUM OF THE VILLUS OF THE MUCOUS MEMBRANE OF THE DUODENUM OF RATS IN THE CONDITIONS OF EPICHLOROHYDRIN AND DRUG INFLUENCE]

Purpose of the research is to study the nature of the disorders of the villi of the duodenal mucous membrane (MM) in conditions of long-acting ECH as well as to substantiate experimentally the effectiveness of the use of the extract of Echinacea purpurea (EP) and thiotriazoline for the purpose of these disorders correction. The withdrawal of the rats from the experiment was carried out on the 1st, 7th, 15th, 30th and 60th day after the completion of the administration of ECH, EP extract and thiotriazoline. Histological processing of duodenum fragments was performed according to the standard method. The cell composition of the villus epithelium of duodenal MM was evaluated using a laboratory microscope of the MC 100 (Micros, Austria) and the Microvisible software (version 1.11.10). The determination of the significance of differences was carried out according to the Mann-Whitney U criterion. Differences were considered significant at p<0.05. Prolonged action of ECH led to a decrease in the number of cells in one villus of duodenal MM. This decrease persisted after the end of the administration of this chemical. There was a decrease in the number of columnar epithelial cells, goblet exocrinocytes and argyrophil endocrinocytes. In rats that did not receive ECH, administration of an EP extract was accompanied by a short-term increase in the number of columnar epithelial cells in one villus of duodenal MM. The administration of thiotriazolin to rats that did not receive ECH caused a short-term increase in the number of cells in one villus of duodenal MM and the number of columnar epithelial cells in the one villus of duodenal MM. The use of EP extract on the background of inhalations of ECH reduced the degree of decrease in the number of cells in one villus of duodenal MM and the number of columnar epitheliocytes in one villus of duodenal MM, reduced the degree and duration of reduction in the number of goblet exocrinocytes in one villus of duodenal MM, reduced the duration of reduction in the number of argyrophil endocrinocytes in one villus of duodenal MM. The use of thiotriazolin during the administration of ECH led to a decrease in the degree and duration of a decrease in the number of cells in one villus of duodenal MM and the number of columnar epithelial cells in one villus of duodenal MM, and also prevented the occurrence of a decrease in the number of goblet exocrinocytes and argyrophil endocrinocytes in one villus of duodenal MM.

Impacts of epichlorohydrin-dimethylamine on coagulation performance and membrane fouling in coagulation/ultrafiltration combined process with different Al-based coagulants

Two kinds of aluminum-based coagulants and epichlorohydrin-dimethylamine (DAM-ECH) were used in the treatment of humic acid-kaolin simulated water by coagulation-ultrafiltration (C-UF) hybrid process. Coagulation performance, floc characteristics, including floc size, compact degree, and strength were investigated in this study. Ultrafiltration experiments were conducted by a dead-end batch unit to implement the resistance analyses to explore the membrane fouling mechanisms. Results showed that DAM-ECH aid significantly increased the UV254 and DOC removal efficiencies and contributed to the formation of larger and stronger flocs with a looser structure. Aluminum chloride (Al) gave rise to better coagulation performance with DAM-ECH compared with poly aluminum chloride (PACl). The consequences of ultrafiltration experiments showed that DAM-ECH aid could reduce the membrane fouling mainly by decreasing the cake layer resistance. The flux reductions for PACl, Al/DAM-ECH (dosing both Al and DAM-ECH) and PACl/DAM-ECH (dosing both PACl and DAM-ECH) were 62%, 56% and 44%, respectively. Results of this study would be beneficial for the application of PACl/DAM-ECH and Al/DAM-ECH composite coagulants in water treatment processes.

Effect of colestimide on the concentrations of polychlorinated dibenzo-p-dioxins, polychlorinated dizenzofurans, and polychlorinated biphenyls in blood of Yusho patients

BACKGROUND

Oral colestimide was reported to lower the concentration of PCDDs, PCDFs, and PCB in the blood of humans. A pilot study showed that the arithmetic mean total TEQ concentrations of PCDDs, PCDFs, and PCBs in the blood of subjects after the trial decreased approximately 20 % compared to pre-trial levels, suggesting that colestimide could decrease human dioxin levels. We designed the current clinical trial study based on this information. In this study, we examined whether colestimide could reduce the individual congener concentrations of PCDDs, PCDFs, and PCBs in the blood of Yusho patients.

METHODS

Out of the 36 Yusho patients who participated in the clinical trial, 26 patients self-administered colestimide 3 g/day orally for 6 months. The concentrations of PCDDs, PCDFs and PCBs in the blood of 26 Yusho patients before the trial were compared with those after the trial.

RESULTS

The arithmetic mean total TEQ concentrations of PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs in the blood of the 26 Yusho patients before and after the clinical trial were 42-303 (mean: 130, median: 120) and 43-283 (mean: 132, median: 118) pg TEQ/g lipid, respectively. The sums of the concentrations of 58 PCB congeners measured in the blood of Yusho patients before and after the trial were 321-2643 (mean: 957, median: 872) and 286-2007 (mean: 975, median: 806) ng/g lipid, respectively, indicating that the concentrations of PCDDs, PCDFs, and PCBs after the trial were almost the same as those before the trial. Among congeners of PCDDs, PCDFs, dioxin-like PCBs, and non-dioxin-like PCBs, most congeners of these compounds did not show a statistically significant decrease after the trial.

CONCLUSION

Colestimide may not be beneficial in reducing the high blood levels of dioxin-like compounds in Yusho patients.

Intestinal Bile Acid Composition Modulates Prohormone Convertase 1/3 (PC1/3) Expression and Consequent GLP-1 Production in Male Mice

Besides an established medication for hypercholesterolemia, bile acid binding resins (BABRs) present antidiabetic effects. Although the mechanisms underlying these effects are still enigmatic, glucagon-like peptide-1 (GLP-1) appears to be involved. In addition to a few reported mechanisms, we propose prohormone convertase 1/3 (PC1/3), an essential enzyme of GLP-1 production, as a potent molecule in the GLP-1 release induced by BABRs. In our study, the BABR colestimide leads to a bile acid-specific G protein-coupled receptor TGR5-dependent induction of PC1/3 gene expression. Here, we focused on the alteration of intestinal bile acid composition and consequent increase of total TGR5 agonistic activity to explain the TGR5 activation. Furthermore, we demonstrate that nuclear factor of activated T cells mediates the TGR5-triggered PC1/3 gene expression. Altogether, our data indicate that the TGR5-dependent intestinal PC1/3 gene expression supports the BABR-stimulated GLP-1 release. We also propose a combination of BABR and dipeptidyl peptidase-4 inhibitor in the context of GLP-1-based antidiabetic therapy.

Bile acid sequestrants: glucose-lowering mechanisms and efficacy in type 2 diabetes

Bile acids are synthesized in the liver from cholesterol and have traditionally been recognized for their role in absorption of lipids and in cholesterol homeostasis. In recent years, however, bile acids have emerged as metabolic signaling molecules that are involved in the regulation of lipid and glucose metabolism, and possibly energy homeostasis, through activation of the bile acid receptors farnesoid X receptor (FXR) and TGR5. Bile acid sequestrants (BASs) constitute a class of drugs that bind bile acids in the intestine to form a nonabsorbable complex resulting in interruption of the enterohepatic circulation. This increases bile acid synthesis and consequently reduces serum low-density lipoprotein cholesterol. Also, BASs improve glycemic control in patients with type 2 diabetes. Despite a growing understanding of the impact of BASs on glucose metabolism, the mechanisms behind their glucose-lowering effect in patients with type 2 diabetes remain unclear. This article offers a review of the mechanisms behind the glucose-lowering effect of BASs, and the efficacy of BASs in the treatment of type 2 diabetes.

Hypoglycemic effects of colestimide on type 2 diabetic patients with obesity

Recent studies have shown colestimide, a bile acid-binding resin, to also exert a glucose-lowering effect via amelioration of insulin resistance. To evaluate the effects of colestimide on glucose metabolism and to elucidate the underlying mechanism, we conducted a 6-month, open-label pilot study on 43 type 2 diabetic patients with obesity (BMI ≥ 25). The subjects were randomized to either treatment with colestimide 4g/day (T group, n=23) or continuation of their current therapy (C group, n=20). In the T group patients, mean HbA1c and fasting glucose improved markedly (from 7.71 ± 0.32% to 6.97 ± 0.20%; from 147.4 ± 7.3mg/dL to 127.0 ± 5.0mg/dL, respectively), while obesity-related parameters, i.e. body weight, waist circumference, and visceral fat and subcutaneous fat as determined by umbilical slice abdominal CT, showed no significant changes. Fractionation analyses of serum bile acids revealed significantly increased cholic acids (CA) and decreased chenodeoxycholic acids (CDCA) in the T group patients. However, no correlation was observed between these changes and ΔHbA1c. According to logistic regression analysis, baseline HbA1c was the only variable predicting the decrease of HbA1c (>0.5%) among sex, age, BMI, total cholesterol, ΔCA and ΔCDCA. The index of insulin resistance, i.e. HOMA-R, did not improve, and the index of β cell function, i.e. HOMA-β, actually increased significantly. These results suggests that, in obese patients with type 2 diabetes, the mechanism underlying improved glycemic control with colestimide treatment involves enhanced β cell activity rather than improved insulin resistance.

Glucose-lowering effect of colestimide is associated with baseline HbA1c in type 2 diabetic patients with hypercholesterolemia

We previously reported that colestimide, an anion exchange resin, improved glycemic control in patients with type 2 diabetes. However, the factors associated with the decrease of HbA1c remain unclear. In present study, we retrospectively compared glycemic control between groups receiving colestimide (n=71), atorvastatin (n=99), pravastatin (n=85), and pitavastatin (n=95) until 3 months after the start of treatment. In the colestimide group, fasting plasma glucose decreased significantly from 169 ± 59 to 138 ± 29 mg/dL after 3 months (P<0.01), and glycated hemoglobin (HbA1c) declined from 8.1 ± 1.0% to 7.4 ± 0.8% (an 8% reduction, P<0.01). Fasting plasma glucose and HbA1c did not change in the pravastatin and pitavastatin groups. On the other hand, both parameters increased significantly in the atorvastatin group. Multivariate analysis revealed that baseline HbA1c was the main determinant of the decrease of HbA1c in the colestimide group while age, sex, BMI, and baseline lipid levels were not correlated with the effect of colestimide treatment. The decrease of HbA1c showed a positive correlation with baseline HbA1c (r=0.60, P<0.0001), and patients with a larger change of HbA1c (>8.4%) displayed a better response to colestimide. In conclusion, since patients with type 2 diabetes often have hyperlipidemia as well, colestimide therapy may have a clinically useful dual action in such patients. Baseline HbA1c has the most important independent influence on the glucose-lowering effect of colestimide.

Sterol Regulatory Element-binding Protein-2- and Liver X Receptor-driven Dual Promoter Regulation of Hepatic ABC Transporter A1 Gene Expression

ABC transporter A1 (ABCA1) mediates and rate-limits biogenesis of high density lipoprotein (HDL), and hepatic ABCA1 plays a major role in regulating plasma HDL levels. HDL generation is also responsible for release of cellular cholesterol. In peripheral cells ABCA1 is up-regulated by the liver X receptor (LXR) system when cell cholesterol increases. However, cholesterol feeding has failed to show a significant increase in hepatic ABCA1 gene expression, and its expression is up-regulated by statins (3-hydroy-3-methylglutaryl-CoA reductase inhibitors), suggesting distinct regulation. In this study we investigated the mechanism of regulation of the rat hepatic ABCA1 gene and identified two major ABCA1 transcripts and two corresponding promoter regions. Compactin activated the novel liver-type promoter in rat hepatoma McARH7777 cells by binding the sterol regulatory element-binding protein-2 (SREBP-2). In contrast, compactin repressed the previously identified peripheral-type promoter in an LXR-responsive element-dependent but not E-box-dependent manner. Thus, compactin increased the liver-type transcript and decreased the peripheral-type transcript. The same two transcripts were also dominant in human and mouse livers, whereas the intestine contains only the peripheral-type transcript. Treatment of rats with pravastatin and a bile acid binding resin (colestimide), which is known to activate SREBP-2 in the liver, caused a reduction in the hepatic cholesterol level and the same differential responses in vivo, leading to increases in hepatic ABCA1 mRNA and protein and plasma HDL levels. We conclude that the dual promoter system driven by SREBP-2 and LXR regulates hepatic ABCA1 expression and may mediate the unique response of hepatic ABCA1 gene expression to cellular cholesterol status.

Fluvastatin Alters Platelet Aggregability in Patients With Hypercholesterolemia

BACKGROUND

Hypercholesterolemia enhances platelet aggregability. Statins have beneficial effects on cardiovascular events. The purpose of this study is to investigate whether statins inhibit platelet aggregation and, if so, the mechanisms.

METHODS AND RESULTS

Twelve patients with hypercholesterolemia were prospectively randomized in a crossover design to receive either fluvastatin (20 mg/d) or colestimide (3000 mg/d) for 12 weeks. The subjects were switched to the opposite arm for additional 12 weeks. Before and after first and second treatments, experiments were performed. Eleven age-matched volunteers with normal lipid profiles served as controls. ADP-induced platelet aggregation, platelet-derive nitric oxide (PDNO) release, intraplatelet levels of GSH and GSSG, and intraplatelet nitrotyrosine production during platelet aggregation were measured. Fluvastatin and colestimide equally lowered total and low density lipoprotein cholesterol levels in hypercholesterolemia. Platelet aggregation was greater in hypercholesterolemia than in normocholesterolemia before treatment and was altered by fluvastatin. PDNO release, intraplatelet glutathione level, and GSH/GSSG ratio were lower in hypercholesterolemia than in normocholesterolemia before treatment and were increased by fluvastatin. Intraplatelet nitrotyrosine formation was greater in hypercholesterolemia than in normocholesterolemia, and decreased by fluvastatin. Colestimide did not have such effects. In vitro application of fluvastatin dose-dependently inhibited platelet aggregation. Furthermore, in vitro application of fluvastatin dose-dependently inhibited platelet nitrotyrosine expressions and the inhibitory effects by fluvastatin were reversed by preincubation with geranylgeranylpyrophosphate.

CONCLUSIONS

Fluvastatin altered platelet aggregability in hypercholesterolemic patients in a cholesterol-lowering independent manner, which was partly mediated by the improvement of intraplatelet redox imbalance.

Effect of colestimide therapy for glycemic control in type 2 diabetes mellitus with hypercholesterolemia

Colestimide is a new anion-exchange resin used to lower serum cholesterol in Japan. Because of its excellent compliance, colestimide can replace cholestyramine. To clarify the effect of colestimide on glycemic controls, colestimide (3 g/day) or pravastatin (10 mg) was given orally to patients with type 2 diabetes treated with oral hypoglycemic agents or insulin who had low-density lipoprotein (LDL) cholesterol levels exceeding 3.6 mmol/l. In the colestimide groups, fasting plasma glucose concentrations had decreased significantly from 8.5 +/- 1.4 to 7.7 +/- 1.5 mmol/l at 3 months (P<0.05), as had glycated hemoglobin (HbA1c) from 7.7 +/- 0.7% to 6.8 +/- 0.5%, for an 8% reduction (P<0.01). Fasting plasma glucose and HbA1c did not change in the pravastatin group. Total cholesterol and LDL-cholesterol decreased significantly (P<0.01) with either medication, with similar reduction rates for both drugs. Doses of oral hypoglycemic agents and insulin did not change during the study, and body weight remained stable. Considering that patients with type 2 diabetes often have hyperlipidemia, colestimide therapy may have a clinically useful dual action in such patients.

Biosorption of lead ion by chemically-modified biomass of marine brown algae Laminaria japonica

In this paper, marine brown algae Laminaria japonica was chemically-modified by crosslinking with epichlorohydrin (EC(1), EC(2)), or oxidizing by potassium permanganate (PC), or only washed by distilled water (DW). They were used for equilibrium sorption uptake studies with lead. As can be seen from the experimental results that biosorption equilibriums were rapidly established in about 2h. The lead adsorption was strictly pH dependent, and maximum removal of lead on biosorbents were observed at pH 5.3. The effects solid/liquid ratio on lead biosorption was also investigated. The maximum lead uptakes were 1.67 mmol g(-1), 1.62 mmol g(-1), 1.54 mmol g(-1) and 1.21 mmol g(-1), respectively for EC(1), EC(2), PC and DW. The order of maximum lead uptakes for different pretreated and raw alga was EC(1)>EC(2)>PC>DW. A comparison of different isotherm models revealed that the combination of Langmuir and Freundlich (L-F) isotherm model fitted the experimental data best.

Effects of colestimide and/or Bofu-tsusho-san on plasma and liver lipids in mice fed a high-fat diet

Hypercholesterolemia is known to enhance the risk of coronary heart disease and fatty liver. Colestimide is an anion-exchange resin, which is not absorbed in the small intestine, decreases the intestinal reabsorption of bile acids synthesized from cholesterol in the liver and consequently increases bile acid excretion into the feces. Bofu-tsusho-san, a traditional Japanese herbal remedy, contains 18 components and has long been used as an anti-obesity agent. In the present study, we investigated the effects of colestimide and/or Bohu-tsusho-san in young male mice fed a high-fat diet. The high-fat diet supplemented with both colestimide and Bofu-tsusho-san markedly reduced the plasma levels of lipids, the liver weight and number of fatty droplets in the liver cytoplasm, and the body growth, compared with animals fed a high-fat diet alone. Neither medicine affected the blood biochemistry. Thus, the hypocholesterolemic action of colestimide, sometimes bringing light flatulence, which is improved by simultaneous administration of Bofu-tsusho-san, which activates the thermogenesis of brown adipose tissue, is suggested to reduce body mass and liver lipids, lowering the plasma levels of lipids.

Usefulness of preheparin lipoprotein lipase mass as a parameter for predicting the efficacy of colestimide

This study was conducted to clarify the characteristics of colestimide responders. Forty-seven non-diabetic patients with high levels of low-density lipoprotein cholesterol (LDL-C) received colestimide at 3,000 mg/day and were followed up for 4 months. After 4 months, body weight was reduced but the change was not statistically significant. Total serum cholesterol (TC) and LDL-C levels significantly decreased from 280 to 232 mg/dl and from 195 to 150 mg/dl, respectively (p<0.01 versus before colestimide was administered). Serum triglyceride (TG) levels increased, but the change was not significant. Preheparin lipoprotein lipase mass (preheparin LPL mass) at baseline was significantly higher in colestimide responders (greater than a 20% decrease of LDL-C: n=28) than non-responders (76.2 ng/ml versus 50.3 ng/ml, p<0.05: n=19). Next, the subjects were divided into those with a high (n=33) and low (n=14) preheparin LPL mass at baseline. LDL-C levels were significantly decreased in patients with a high preheparin LPL mass while TG levels were significantly increased in patients with a low preheparin LPL mass. These results suggest that baseline preheparin LPL mass may be a marker of the response to colestimide.

Effect of Oral Colestimide on the Elimination of High-dose Methotrexate in Patients With Primary Central Nervous System Lymphoma-Two Case Reports-

Delayed methotrexate (MTX) elimination occurred in two patients with primary central nervous system lymphoma undergoing high-dose MTX treatment. Oral administration of the anion exchange resin colestimide, which binds MTX effectively in vitro, effectively accelerated MTX elimination. Colestimide probably interrupts the enterohepatic circulation, and is a potential oral antidote to MTX toxicity.

Use of epichlorohydrin-treated chitosan resin as an adsorbent to isolate kappa-casein glycomacropeptide from sweet whey

This study was undertaken to develop a method to isolate glycomacropeptide (GMP), a bioactive compound, from sweet whey by using chitosan resins as anion exchangers. Shrimp shells were used to prepare two chitosan (polyglucosamine) resins, one with the primary amine (-NH(2)) (resin A) and the other with the secondary amine (-NH-) (resin B) as the major functional group. These resins were tested as adsorbents for the isolation of GMP from sweet whey, and the results obtained were compared with those obtained with commercial anion exchangers. The most important finding in this experiment was that the GMP binding capacity of resin A was much higher than that of resin B. Resin A may be the anion exchanger to be tested for industrial scale production of GMP. Amino acid analysis of the GMP-depleted whey fraction suggests that this product can replace sweet whey as an ingredient in various food products including infant formulas, bakery products, and beverages.

32P-post-labelling of 7-(3-chloro-2-hydroxypropyl)guanine in white blood cells of workers occupationally exposed to epichlorohydrin

Epichlorohydrin (ECH) is a simple 3-carbon epoxide of industrial importance. It has been shown to be genotoxic in several systems and carcinogenic in experimental animals. The aim of the present investigation was to study DNA adducts of ECH as a biomarker of occupational exposure to this chemical. 7-(3-Chloro-2-hydroxypropyl)guanine (7-CHP-guanine) was analysed in DNA from white blood cells using an anion exchange-based adduct enrichment protocol of the (32)P-post-labelling/HPLC-based assay. Blood samples were collected from seven workers handling ECH (exposed), nine workers not handling ECH but normally present in the premises where this chemical is used (potentially exposed) and 13 office and factory workers from locations in the plant where ECH is not handled (controls). 7-CHP-guanine was detected in five of the seven workers exposed to ECH (1.6-7.1 mol/10(9) mol nucleotides) and in two of the nine workers potentially exposed to ECH (0.8-1.5 mol/10(9) mol nucleotides). This adduct was not detected in any of the 13 controls. The difference in adduct levels between exposed workers and controls was statistically significant (Mann-Whitney test, P < 0.001), as was the difference between exposed workers and potentially exposed workers (P = 0.017). The recovery of 7-CHP-guanine in the (32)P-post-labelling assay was on average 48 +/- 7%, which is considerably higher than previously reported for other 7-alkylguanines. The method used had a limit of detection of approximately 0.4 mol adduct/10(9) mol nucleotides using 20 microg DNA. This study shows for the first time ECH-induced DNA adducts in humans and suggests that 7-CHP-guanine may be used as a biomarker of occupational exposure to ECH.

Epichlorohydrin induced biochemical changes in the rose-ringed parakeet, Psittacula krameri Scopoli

Intraperitoneal administration of epichlorohydrin (ECH) at the dose level of 20 and 50 mg/kg body weight inhibited spermatogenesis in the testis of parakeet during breeding season. A total load of 60 mg/kg body weight of ECH given on 3 consecutive days proved to be lethal. Testicular proteins, nucleic acids (DNA and RNA), phospholipids and acid phosphatase activity were decreased, while the lipids, total cholesterol and alkaline phosphatase activity increased after ECH administration. The results suggest that the testicular atrophy caused by ECH was associated with an alteration in the activities of macromolecules and enzymes related to specific events of spermatogenesis.

Effects of three epoxides--ethylene oxide, propylene oxide and epichlorohydrin--on cell cycle progression and cell death in human diploid fibroblasts

Ethylene oxide (EtO), propylene oxide (PO), and epichlorohydrin (ECH) strongly influenced the G1/S progression in human diploid fibroblasts, VH-10. However, these epoxides did not affect substantially the G2/M progression. It was found that G1 arrest is induced by these epoxides 6-18 h after the treatment at doses above 5, 3, and 0.5 mMh for EtO, PO, and ECH, respectively. An inhibitory effect on DNA synthesis was also demonstrated at the same doses within the same time interval. On the contrary, the epoxides transiently stimulated DNA synthesis 3-18 h after the treatment with the lower doses (below 5, 3, and 0.5 mMh for EtO, PO, and ECH, respectively). This effect was manifested both as an elevated rate of DNA synthesis and as an increase in the number of cells in S-phase. Among the three studied epoxides EtO was the most effective one: the increases of the rate of DNA synthesis and of cells in S-phase were 35 and 55%, respectively. All the epoxides tested induced significant decrease of intracellular level of reduced glutathione (GSH) shortly after cell exposure. While low and moderate doses induced a transient decrease in GSH level the high doses induced its irreversible depletion. The extensive GSH depletion was related to cell death. Morphological examination of cell nuclei indicated that epoxide-treated cells die via necrosis. This conclusion is supported by the lack of such features of the apoptosis as chromatin condensation and the occurrence of so called 'apoptotic bodies'. The absence of nucleosomal fragmentation of DNA and an increase of the permeability of the plasma membrane after the epoxide treatment also indicated a necrotic form of cell death. ECH is about ten times more toxic than the two other epoxides, and it causes almost 100% necrosis at dose of 3.0 mMh.

Adducts with haemoglobin and with DNA in epichlorohydrin-exposed rats

Epichlorohydrin (1-chloro-2,3-epoxypropane; ECH) is an important industrial chemical and a carcinogen in experimental animals. The main aims of the present study were to characterize the adduct formation in female Wistar rats and to identify adducts that could potentially be used in human biomonitoring studies. The total binding of radioactivity to haemoglobin in rats administered 0, 0. 11, 0.22, 0.43, or 0.97 mmol [3H]ECH/kg body weight by i.p. injection, and sacrificed 24 h after treatment, was linearly related to a dose up to 0.43 mmol/kg body weight. The binding at the highest dose was higher than predicted by extrapolation from lower doses, indicating saturation of a metabolic process for elimination of ECH. Ion-exchange chromatography of a globin hydrolysate showed one major radioactivity peak corresponding to S-(3-chloro-2-hydroxypropyl)cysteine. The half-life of this adduct was estimated as about 4 days by analysis of globin from rats administered 0.43 mmol/kg body weight and sacrificed after 1, 2 and 9 days. Crosslinking of the adduct, presumably with glutathione, appeared to be the predominant secondary reaction. Hydrolysis of N-(3-chloro-2-hydroxypropyl)valine, the primary reaction product of ECH with N-terminal valine, would give N-(2,3-dihydroxypropyl)valine. A sensitive gas chromatography/mass spectrometry method for the dihydroxypropyl adduct was used to follow its formation and removal after administration of nonlabelled ECH (0.11 mmol/kg body weight). The level of this adduct reached a maximum of about 20 pmol/g globin after a few weeks, corresponding to about 0.1% of the initial binding of ECH to globin. N-7-(3-Chloro-2-hydroxypropyl)guanine was detected in rats administered 0.97 mmol [3H]ECH/kg body weight and sacrificed 6 h after treatment. The adduct levels in haemoglobin and DNA were compared with previously reported adduct levels in male Fischer 344 rats exposed to propylene oxide. Despite its higher chemical reactivity, the capacity of ECH to alkylate macromolecules in vivo was found to be somewhat lower than that of propylene oxide.

Rejoining of DNA strand breaks induced by propylene oxide and epichlorohydrin in human diploid fibroblasts

The repair kinetics of DNA single- and double-strand breaks (SSBs, DSBs) induced with two carcinogenic epoxides, propylene oxide (PO) and epichlorohydrin (ECH), was studied in human diploid fibroblasts. The methods used were: alkaline DNA unwinding (ADU), the comet assay, and pulsed field gel electrophoresis (PFGE). About 70% of SSBs, measured by ADU, were rejoined after the treatment with 5 mMh and 10 mMh of PO within 20 hr, and the half-life was estimated to be approximately 15 hr. On the other hand, effective rejoining of SSBs after ECH treatment was observed only at a dose of 1 mMh (a half-life of approximately 15 hr), whereas after 2 mMh treatment, only 26% of SSBs could be rejoined within 20 hr. Furthermore, the use of the comet assay demonstrated that DNA strand breaks were effectively rejoined after PO and ECH treatment at doses of 5-10 mMh and 0.5-1 mMh, respectively. About 76% and 83% of DSBs induced by 5 and 10 mMh of PO, respectively, were rejoined within 4 hr after the treatment (a half-life of approximately 2.5 hr), with little further repair thereafter. At lower dose of ECH (1 mMh) a half-life for DSBs rejoining was estimated to be approximately 2 hr; however, only 29% of DSBs were rejoined within 2 hr at the higher dose of 2 mMh. After 18 hr, the rejoining following treatment with a lower dose was negligible. At a higher dose, a rapid accumulation of DSBs was observed, probably as the result of cell death and DNA degradation. The results demonstrate the capability of human diploid fibroblasts to repair DNA SSBs and DSBs at low-to-moderate doses of the epoxides. A weak capacity to rejoin DNA strand breaks induced by higher doses of ECH may be a consequence of its higher DNA alkylation activity and approximately 10 times higher toxicity compared to PO.

Monitoring of occupational exposure to epichlorohydrin by genetic effects and hemoglobin adducts

The present work is focused on the determination of in vivo doses and studies of genetic effects in workers exposed to epichlorohydrin (ECH). The studied endpoints were hemoglobin (Hb) adducts, frequencies of hprt mutants, micronuclei in cytochalasin B blocked binucleated lymphocytes, sister chromatid exchanges (SCE) and high frequency cells (HFC). Blood samples were collected from office clerks and ECH exposed factory workers at an industrial plant in Germany. The workers were exposed to 0.11-0.23 ppm ECH in the air 45 h per week and to 0.2-2.6 ppm for 3 h per week. Some Swedish non-exposed subjects were also used for Hb adduct measurements. The genetic data, HFC and SCE, showed a significant difference between exposed and unexposed donors. In contrast to earlier studies on SCE, no impact of smoking was observed. Effects on micronuclei were on the borderline of significance, whereas there was no effect for HPRT mutants. The average Hb adduct level was higher in exposed than in non-exposed donors, although the difference was only significant when the exposed group was compared to Swedish controls. Smoking gave significantly increased adduct levels. The absence of significant correlations between individual data for Hb adducts and genetic effects, may be explained by the different periods of time covered by the responses in these endpoints. Whereas Hb adducts reflect the exposure during up to 4 months (i.e. the life span of human erythrocytes), the SCE, and particularly the HFC, seem to accumulate for years in a long-lived fraction of T-lymphocytes without DNA repair. Thus, the adduct data does not reflect the exposure backwards in time unless it can be shown that exposure conditions have remained unchanged. The origin of the background adduct levels in non-smoking control persons is at present not known.

[Ontogenetic characteristics of the body response to chronic exposure to chemical substances]

Chronic intoxication by carbon oxide and long-term exposure to hypoxic hypoxia produced more favourable reactions in animals, exposed to these in the early terms of ontogenesis. The observed regularity was not found under chronic exposure to styrene and epichlorohydrin ++. A supposition is made on the evolutionary predetermination of this effect pertaining to unfavourable factors of hypoxic nature.

Enhancement of cyclosporin production in a Tolypocladium inflatum strain after epichlorohydrin treatment

Following treatment of conidia of the cyclosporin producer fungus, Tolypocladium inflatum, with 0.15 M epichlorohydrin, strain M6 was isolated. The new strain exhibited a similar growth rate to the parent organism but more extensive conidiation and several-fold higher overall cyclosporin production. Strain M6 reached titres of 318 mg l-1 cyclosporin A in agar cultures, whereas in liquid medium it produced 140 mg l-1 cyclosporin A and 68 mg l-1 cyclosporin C. It also maintained a steady volumetric productivity of 0.48 mg l-1 h-1 cyclosporin A over 2 weeks of submerged cultivation in maltose-based semisynthetic medium. The new strain holds potential for improved cyclosporin production due to the superior titres and demonstrated capacity to sustain elevated production of cyclosporin for periods greater than the wild type.

The automated analysis of rat sperm motility following subchronic epichlorohydrin administration: methodologic and statistical considerations

The automated analysis of sperm motion endpoints is potentially useful in identifying male reproductive toxicants and ultimately in predicting fertility in humans. The present study was designed to evaluate the automated analysis of rat sperm motility characteristics following subchronic administration of epichlorohydrin. This type of validation is a prerequisite for inclusion of sperm motion measurements in the process of reproductive risk assessment. In the present studies videotapes were made of cauda epididymal spermatozoa from Long-Evans rats, both untreated and treated with epichlorohydrin. From analysis of videotapes of control epididymal spermatozoa, the relationship of various sperm motion endpoints and settings of the CellSoft computer-assisted sperm motion analysis system (Cryo Resources, Ltd., New York, NY) is described. Optimal settings of the system for analysis of rat spermatozoa are detailed. Employing data from both control and epichlorohydrin-treated animals, a statistical methodology is described that evaluates: (1) the distributions of CellSoft generated sperm motion endpoints, (2) the correlations between these endpoints, and (3) techniques for detection of dose-related effects.

An in vivo unscheduled DNA synthesis (UDS) assay in the rat gastric mucosa: preliminary development

A new in vivo unscheduled DNA synthesis (UDS) assay is described for the detection of genotoxic damage in the rat stomach. In this assay advantage is taken of the morphology of the gastric mucosa to enable the selective isolation, and subsequent measurement of UDS, in non-S-phase cells. The absence of replicating cells allows UDS to be measured by scintillation counting without having to use hydroxyurea. Control background responses are given, these were low and acceptably stable. The sensitivity of the assay was tested using 1-methyl-3-nitro-1-nitrosoguanidine which was found positive at doses as low as 12.5 mg/kg. The selectivity of the assay for genotoxins was tested using indomethacin, a nongenotoxic, gastric irritant. This compound was negative at dose levels and exposure times known to produce gastric lesions. Two forestomach-specific carcinogens, aristolochic acid and epichlorhydrin, were also investigated. Aristolochic acid was, surprisingly, uniformly negative. Further work on this compound is obviously required especially in the light of the strong positive response produced by epichlorhydrin. These data would suggest that this assay would be a useful complement to the current in vivo short-term test battery and a helpful research tool for investigating DNA repair in stomach tissue.

Bile acid binding and hypocholesterolemic activity of a new anion exchange resin from 2-methylimidazol and epichlorohydrin

A new anion exchange resin with an imidazolium salt on a epoxide polymer skeleton was synthesized. This white powder material was odorless and tasteless. The in vitro sodium cholate binding of this resin was much more potent than that of cholestyramine. The hypocholesterolemic activity of this resin in cholesterol-fed rabbits proved to be 4.3 times more potent than that of cholestyramine. These results suggest that effective reduction of plasma cholesterol may be achieved with lower doses of this resin.

Forestomach carcinogens: pathology and relevance to man

Squamous cell carcinomas of the forestomach have been observed in many carcinogenicity studies in rodents, especially after oral or gavage exposure. The histopathological diagnosis of forestomach lesions and the relevance of the data for human risk estimation can be controversial. The pathological classification may be troublesome because of the low-grade malignancy and the pseudoepitheliomatous hyperplasia that may develop after ulceration and inflammation. For human risk estimation it is important to understand the mechanism of action; this is illustrated by examples using butylated hydroxyanisole, methyl bromide, and epichlorohydrin. Another feature that complicates risk estimation is the absence of a homologue for the forestomach in man. The potential risk from non-genotoxic forestomach carcinogens in man involves exposure of the mouth, pharynx, and esophagus at dose levels that exert irritating action. It is assumed that exposure to non-genotoxic chemicals at concentrations far below those having irritating potential is not hazardous to humans.

A method for assessing damage to mitochondrial DNA caused by radiation and epichlorohydrin

This paper describes a rapid and reliable method for quantification of damage to mitochondrial DNA (mtDNA), especially strand breaks. The degree of damage to mtDNA is assessed by the proportion of physical forms (i.e., supercoiled versus open-circular and linear forms) upon agarose gel electrophoresis, blotting, and visualization by hybridization with [32P]mtDNA probes. The use of a radiolabeled probe is a crucial step in the procedure because it provides both a means to quantify by radioautography and to obtain the mtDNA specificity required to eliminate misinterpretation due to nuclear DNA contamination. To demonstrate the utility of this technique, X-irradiation and epichlorohydrin are shown to damage both isolated mtDNA and mtDNA in whole cells in a dose-dependent fashion.

Characterization and quantitation of 3-alkylthymidines from reactions of mutagenic propylene oxides with thymidine

Thymidine was reacted in methanol with four epoxides of varying mutagenicities: propylene oxide, glycidol, epichlorohydrin and trichloropropylene oxide. A single product was detected with each epoxide, and these products had the same retention times on silica high pressure liquid chromatography (HPLC). UV spectra of the products identified them as 3-alkylthymidines, and this was confirmed by infrared (IR) and nuclear magnetic resonance (NMR) spectra. Mass spectra (MS) analysis showed the products to be consistent with attachment at the least substituted carbon of the epoxide. Formation of 3-alkylthymidines correlated to Taft sigma electron withdrawing values for the substituents on the epoxides and mutagenicities in strain TA100 of the Ames Assay.

In vivo and in vitro binding of epichlorohydrin to nucleic acids

Epichlorohydrin (EC) binds to macromolecules of biological relevance in vivo: DNA is less labelled than RNA and proteins, rat organs interact more than mouse organs, stomach is the most labelled organ with liver, kidney and lung involved in decreasing order. Based on the Covalent Binding Index (CBI), EC is a weak-moderate oncogen, just as other chlorinated hydrocarbons such as 1,2-dichloroethane and carbon tetrachloride. An interaction of EC with nucleic acids (DNA and polyribonucleotides) occurs also in vitro. It is mediated either by chemical reactivity per se of the molecule (near-UV (NUV) irradiation does not photoactivate EC) and by enzymatic (microsomal and/or cytosolic) fractions, whose relative effectiveness is variable in relation to the organ tested. The best substrates for interaction are poly(G) and poly(A) when using microsomal and cytosolic fractions, respectively, whereas the labelling of double-stranded DNA is always lower. On the whole, the picture of enzyme (microsome + cytosol)-mediated in vitro interaction is similar to the pattern of in vivo binding, with the exception of rat stomach enzymes which are inactive in vitro.

Evaluation of epichlorohydrin (ECH) genotoxicity. Microsomal epoxide hydrolase-dependent deactivation of ECH mutagenicity in Schizosaccharomyces pombe in vitro

The mutagenic effect of epichlorohydrin (ECH) on the yeast Schizosaccharomyces pombe was studied in vitro in the presence of mouse-liver S9 mix and microsomal and cytosolic fractions. The incubations were always performed in the absence of NADPH-generating systems. S9 mix and microsomes from phenobarbital-pretreated mice significantly reduced ECH mutagenicity, whereas the cytosol did not result in any deactivating effect. The various protein contents of the subcellular fractions were not involved in any scavenger effect as regards ECH mutagenic activity. Moreover, the addition of reduced glutathione to the incubation mixtures indicated that it did not play an important role, either per se or through the enzyme(s) glutathione-S-epoxide transferase(s), in preventing ECH genotoxicity. Our results suggest that microsomal epoxide hydrolase(s) represents the major step in the detoxifying pathway of ECH. These observations were supported by measurements of the specific epoxide hydrolase activity in the various fractions on the same substrate.

In vivo and in vitro mutagenicity studies of a possible carcinogen, trichloroethylene, and its two stabilizers, epichlorohydrin and 1,2-epoxybutane

In vivo and in vitro methodologies that have employed the yeast Schizosaccharomyces pombe as genetic indicator have been utilized to investigate the mutagenicity of two trichloroethylene (TCE) samples of pure and technical grade. Mutagenicity assays were also performed on two stabilizers contained in the technical grade sample: epichlorohydrin and 1,2-epoxybutane. In the in vitro studies a metabolic conversion system was supplied by liver homogenate (S-9) from mice and rats untreated and pretreated with phenobarbital and/or beta-naphthoflavone. Up to highly toxic doses of TCE were applied to growing and stationary-phase yeast cells. In the in vivo studies two different host-mediated assays, intrasanguineous and intraperitoneal methodologies, were performed on different mice breeds treated by oral administration. Epichlorohydrin and epoxybutane were tested singly or combined in a mixture of the same ratio as in the technical grade TCE sample. Both TCE samples gave negative results for in vivo and in vitro assays, whereas the two contaminants were found mutagenic only in vitro. The high toxicity of the technical TCE sample did not allow us to reach concentrations containing effective levels of its two additives.

Comparison of the mutagenic potency of 2-chloroethanol, 2-bromoethanol, 1,2-epoxybutane, epichlorohydrin and glycidaldehyde in Klebsiella pneumoniae, Drosophila melanogaster and L5178Y mouse lymphoma cells

A series of 2 haloethanols and 3 epoxides was investigated in 3 mutagenicity test systems, namely (1) the fluctuation test in Klebsiella pneumoniae, (2) the sex-linked recessive lethal test in Drosophila melanogaster, and (3) the HGPRT test with L5178Y mouse lymphoma cells. The order of mutagenic potency was, in Klebsiella: glycidaldehyde greater than 2-bromoethanol = epichlorohydrin greater than 1,2-epoxybutane greater than 2-chloroethanol; in Drosophila: glycidaldehyde = epichlorohydrin greater than 1,2-epoxybutane; in mouse lymphoma cells: epichlorohydrin greater than 1,2-epoxybutane. The haloethanols were non-mutagenic in Drosophila. 2-Chloroethanol and glycidaldehyde were negative in mouse lymphoma cells. The high mutagenic potency of epichlorohydrin as compared with 1,2-epoxybutane was consistent in all systems, and with published data.

In vitro induction of SCE in human lymphocytes by epichlorohydrin with and without metabolic activation

Human lymphocytes cultured for 73 h in the presence of BrdU were exposed to epichlorohydrin (ECH) with and without metabolic activation. Cells exposed for the entire culture time without activation showed a significant dose related increase in SCE yield. Exposure for the final 25 h only showed a similar response but with increased tolerance. The presence of S9 mix significantly reduced the effect of ECH compared with a similar exposure without activation. Without activation 4 X 10(-4) M ECH produced a 3-fold increase in the incidence of SCE over the control level. However, with S9 mix a concentration of 10(-3) M ECH was required to produce such an increase indicating that S9 mix may have a detoxifying effect.

Cytogenetic analysis of peripheral lymphocytes in workers occupationally exposed to epichlorohydrin

Peripheral lymphocytes of 3 groups of adult subject (28 workers occupationally exposed for 4 years to epichlorohydrin [ECHH], 34 matching controls and 21 subjects of the general population (control group) were cytogenetically analysed. In total, 11 806 metaphases were scored. The following frequencies of aberrant cells (bearing mostly chromatid and chromosome breaks) were detected in individual groups: ECHH-exposed group 3.12%; matching controls 2.06%; general population control group 1.33%. The results seem to indicate that even the concentration of 1 mg ECHH/m3 was capable of increasing the frequency of aberrant cells in the occupationally exposed group of workers.

Rapid slide technique with dextranomer beads for bacteriologic assessment of wounds in the elderly: comparison with quantitative biopsy method

A rapid slide technique to provide quantitative bacteriologic assessment of wounds in elderly and debilitated patients is described. It involves the use of material from dextranomer-bead (Debrisan) wound dressings to replace tissue biopsy for deciding when a wound is ready for closure or when a specific therapy is no longer efficacious. In 27 patients an 81 percent correlation was demonstrated between the bacterial count as determined by the new method and that determined by the more complicated tissue biopsy.

An in vitro chromosome assay using cultured rat-liver cells

An in vitro chromosome assay has been developed which utilises an epithelial-like cell line derived from rat liver. The cell line, designed RL1, retains sufficient metabolic enzyme activity to detect chromosome damage induced by a variety of chemical mutagens and carcinogens without the incorporation of an extrinsic metabolising system. The cells are grown on standard glass microscope slides, exposed to the test chemical and processed in situ for metaphase analysis. In a small validation study, chromosome damage was detected in cultures exposed to the direct-acting agents, methyl nitronitrosoguanine, 4-nitroquinoline-N-oxide, propylene oxide, epichlorohydrin and 1,2:3,4-diepoxybutane and to compounds requiring metabolic activation, including cyclophosphamide, 2-acetylaminofluorene, 3-methylcholanthrene and 7,12-dimethylbenz[a]anthracene. Negative results were obtained with pyrene and carbon tetrachloride.

Mutagenic effect of epichlorohydrin. II. Analysis of chromosomal aberrations in lymphocytes of persons occupationally exposed to epichlorohydrin

A prospective cytogenetic study was conducted in 35 workers occupationally exposed to epichlorohydrin (ECHH). Blood samples for cytogenetic analysis were collected before the exposure (to serve as a control) and after the first and second years of ECHH exposure; the cultivation time was 56--58 h. Four slides from each worker were prepared, coded and two of them separately analysed in two collaborating cytogenetic laboratories. About 50 cells were analysed on each slide, giving a total 16,674 scored cells. The percentage of cells with chromosomal aberrations in blood samples of workers was 1.37 before exposure, 1.91 after the first year and 2.69 after the second year of exposure. The difference between percentages of aberrant cells before and after two years of occupational exposure was highly significant (P less than 0.0001). There was particularly observed an increase of chromatid and chomosomal breaks after exposure, simultaneously with an increased number of breaks per 100 cells. These results are concordant with previously reported cytogenetic data found in experiments with mammals and human cells in vitro.

Cytogenetic analysis of human chromosomes and its value for the estimation of genetic risk

A short review of present-day contradictory opinions on the usefulness of human chromosomal analysis in the system of chemical mutagen testing is illustrated by examples of the results achieved by both conventional and banding techniques. The results include exposures of human chromosomes to ECHH and TEPA in vitro, and to ECHH, vinyl chloride and Imuran in vivo. Exposures of human lymphocytes in vitro to the chemical to be tested for mutagenicity are recommended as one of the tests to be included in the system of mutagenicity testing, parallel with all other tests on mammalian and submammalian levels. The testing of human chromosomes of people exposed to chemicals in vivo is considered essential.

Vinyl chloride mutagenicity via the metabolites chlorooxirane and chloroacetaldehyde monomer hydrate

Mutagenicity tester strains of Bacillus and Salmonella were used to assay vinyl chloride in nutrient broth at a practical concentration level. Also screened without exogenous activation were seven potential metabolites of vinyl chloride in their pure forms as well as the related epichlorohydrin. Chlorooxirane, chloroacetaldehyde, chloroacetaldehyde monomer hydrate, chloroacetaldehyde dimer hydrate, chloroacetaldehyde trimer, and epichlorohydrin produced significant mutagenic acitivity in Salmonella typhimurium strains sensitive to base-pair mutation. A recombination repair deficient strain of Bacillus subtilis was inhibited in growth by these compounds, whereas excision repair deficient and wild type strains of Bacillus subtilis were relatively unaffected. On the basis of these assays a working hypothesis for the vinyl chloride carcinogenesis mechanism is proposed which involves chlorooxirane and chloroacetaldehyde monomer hydrate as the ultimate carcinogenic metabolites of vinyl chloride.

Mutagenic effect of epichlorohydrin. I. Testing on human lymphocytes in vitro in comparison with TEPA

The mutagenic effect of the monofunctional alkylating agent epichlorohydrin was tested on human lymphocytes in vitro and compared with the mutagenic effect of the polyfunctional alkylating agent TEPA. The same descending concentrations were used for both mutagens: 10(-4), 10(-5), 10(-6), 10(-7), 10(-8), 10(-9), 10(-10) and 10(-11) M. Similar types of chromosomal aberration were found, but the effect of ECHH was 4-5 times lower than that of TEPA. ECHH was found to be a mild mutagen. Different timing of mutagen application was used in the course of 56 h of cultivation of lymphocytes: 1 h before cultivation, one hour between the 24th and 25th h of cultivation and 24 h before the end of cultivation. From the results presented we conclude that the application of the chemical for the last 24 h of human lymphocyte cultivation should be recommended for routine mutagenicity testing.

Banding technique used for the detection of chromosomal aberrations induced by radiation and alkylating agents TEPA and epichlorohydrin

Blood samples from two healthy donors were exposed, (1) to 200 R of X-rays in G0 and G1S phases of the cell cycle, and (2) to epichlorohydrin 10(-6) M and TEPA 10(-4) M in G0 and/or in G1S and G2 phases. Part of the cells was processed for chromosome studies conventionally and the other part by the trypsinization banding technique. Detailed chromosomal analysis showed that, after irradiation, 38.2% of aberrations in G0 and 18.7% in G1S phases escaped cytogenetic detection when the conventional technique was used. After exposures to TEPA and ECHH, 10.9% of aberrations were undectable in G0 and 3.3% in G1S and G2 phases. The distribution of chromosome breaks was non-random both after irradiation and after exposure to alkylating agents. However, it differed according to the mutagen used. Some chromosomal segments were broken significantly more frequently than the others (e.g. 9q12), some were resistant to breakage (e.g. the whole Y chromsome). The segments represented by G-negative bands were more fragile than the G-positive and G-variable segments.