Article

Accumulation of ethoxyquin in the tissue

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Abstract

Ethoxyquin (EQ) residue levels in the mouse tissue were determined by the HPLC-fluorometric detection method. Mice were given powdered feed containing 0, 0.125, and 0.5% EQ HCl and the EQ residue levels in liver, kidney, lung, and brain tissues were determined after 2, 4, 6, 10, and 14 wk (4 mice/group). The tissue samples were homogenized in 10 volumes (w/v) of acetonitrile-water (7:3, v/v), centrifuged, and the supernatants were stored in a freezer for 2-3 h or until the two layers separated; then the clear upper layers were analyzed. The mean EQ residue levels in the tissue ranged 0.84-4.58 micrograms EQ/g liver and 0.11-0.92 micrograms EQ/g brain. The relative weight of the liver (5.21-7.07% body weight) and the hepatic glutathione level (5.99-7.83 microM GSH/g tissue) of mice that received EQ were significantly higher than those of the controls (4.67-5.05% body weight and 4.30-5.78 microM GSH/g tissue, respectively). The mean hepatic mitochondrial glutathione level of the higher EQ feeding group, following dietary administration of EQ for 14 wk, was approximately twofold (1.68 nM GSH/mg protein) of both the control and the lower EQ feeding groups (0.83 and 0.74 nM GSH/mg protein, respectively).

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... A large number of experiments have contributed to a general understanding of the metabolic pathways of EQ in mammals (13)(14)(15)(16)(17)(18). However, our knowledge regarding dietary EQ in fish is modest. ...
... LOD for EQ determination in salmon muscle by Skaare and Roald (29) was 0.1 mg/L. Other published data related to this topic are not relevant for comparison because of the higher operational range discussed above and the absence of information about metabolites (13,(19)(20)(21)(22)(23)(27)(28)(29). ...
... The mean recoveries of compounds from spiked samples are shown in Table 1. The average recoveries of EQ and EQ dimer were 19 and 11% higher, respectively, than those reported for other procedures (13,(19)(20)(21)(22)27). However, increases in the average variability to 13% for EQ and 16% for EQ dimer recovery were also noted. ...
Article
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A method for simultaneous quantitative determination of ethoxyquin (EQ) and its major metabolite in Atlantic salmon tissues, ethoxyquin dimer (EQ dimer), has been developed. The separation was achieved on tandem coupled phenyl-hexyl and C18 columns by 2-phase gradient elution with acetonitrile-ascorbic acid-acetic acid-diethyl amine organized in a 23.5 min sequence. Compounds were extracted with hexane from samples saponified in ethanol-NaOH and protected from air- and light-mediated oxidation by addition of saturated ethylenediaminetetraacetic acid, ascorbic acid, and pyrogallol. The identity of peaks was confirmed by spiking samples with standards verified by proton nuclear magnetic resonance spectrometry, mass spectrometry, and high-performance liquid chromatography. The detection limit (at 358/433 nm) of matrix-spiked EQ was 0.02 and 0.06 microg/L for EQ dimer, with 0.5 g sample weighed and resuspension in 0.5 mL hexane. Linearity was in the range of 0.2-175 microg/L for EQ and 0.3-5100 microg/L for EQ dimer. Two more ubiquitous compounds were identified as de-ethylated EQ and quinone imine. Totally, 14 peaks sharing spectral properties of EQ were separated in a single run, including a major peak present in all muscle samples, termed unknown metabolite of EQ (UMEQ). The concentrations of EQ, EQ dimer, and de-ethylated EQ, as well as concentrations of UMEQ (in arbitrary units), in the muscle were correlated to the amount of EQ fed to the salmon, thus indicating their possible metabolic origin. The pattern of 14 peaks in the muscle showed high specificity and could be used to discriminate between wild salmon and salmon fed EQ-supplemented feed. This method will be a useful tool for studying EQ metabolism and kinetics, and for the routine surveillance of residual levels of dietary EQ in farmed Atlantic salmon.
... 29,30) Ethoxyquin is highly lipophilic; therefore, even when administered orally, it easily crosses the BBB and prevents the formation of oxidized lipids in the brain of pathological mouse models. 31) Ethoxyquin protects against peripheral neuropathy in type II diabetes and neurotoxicity during chemotherapy. 16,17) Moreover, it exerts a protective effect by inhibiting ferroptosis in a doxorubicin-induced cardiomyopathy model. ...
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White matter lesions induced by chronic cerebral hypoperfusion can cause vascular dementia; however, no appropriate treatments are currently available for these diseases. In this study, we investigated lipid peroxidation, which has recently been pointed out to be associated with cerebrovascular disease and vascular dementia, as a therapeutic target for chronic cerebral hypoperfusion. We used ethoxyquin, a lipid-soluble antioxidant, in a neuronal cell line and mouse model of the disease. The cytoprotective effect of ethoxyquin on glutamate-stimulated HT-22 cells, a mouse hippocampal cell line, was comparable to that of a ferroptosis inhibitor. In addition, the administration of ethoxyquin to bilateral common carotid artery stenosis model mice suppressed white matter lesions, blood–brain barrier disruption, and glial cell activation. Taken together, we propose that the inhibition of lipid peroxidation may be a useful therapeutic approach for chronic cerebrovascular disease and the resulting white matter lesions. Fullsize Image
... Ethoxyquin (EQ), a synthetic antioxidant, has been used for many years to hinder lipid oxidation in feeds (Błaszczyk, Augustyniak, & Skolimowski, 2013). It has been demonstrated that dietary EQ increases ROS scavenging abilities in the livers of mice and plasma of hens (Felver-Gant, Dennis, Zhao, & Cheng, 2014;Kim, 1991). ...
Article
Firstly, a linoleic acid emulsion and fish hepatopancreas homogenate were incubated with ethoxyquin and the extracts of Angelica sinensis. The results demonstrated that ethoxyquin showed the strongest protective effects against lipid oxidation of all of the examined compounds (p < 0.05). However, ethyl acetate extract of Angelica sinensis at high concentrations showed a stronger effect on lipid oxidation than that of ethoxyquin (p < 0.05). Next, seven experimental diets that contained 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 g/kg of ethyl acetate extract of Angelica sinensis were fed to seven groups of carp (Cyprinus carpio var. Jian) respectively. After 60 days, carp were exposed to 2.4 mg trichlorfon/L in water for 4 days. The results displayed that trichlorfon exposure increased the contents of malonaldehyde and protein carbonyl in digestive organs and the activities of glutamate‐oxaloacetate and glutamate‐pyruvate transaminase in plasma, and decreased feed intake, the level of reduced glutathione, and the activities of trypsin, chymotrypsin, lipase, alpha‐amylase, Na+,K+‐ATPase, alkaline phosphatase, antisuperoxide anion, antihydroxyl radical, superoxide dismutase, glutathione reductase, and glutathione S‐transferase in digestive organs of carp (p < 0.05). Moreover, the dietary ethyl acetate extract of Angelica sinensis prevented the decrease in the above parameters in carp treated with trichlorfon (p < 0.05). These results revealed that the dietary ethyl acetate extract of Angelica sinensis could quench the trichlorfon‐induced structural and functional damage by improving the antioxidative capacity of the digestive organs of fish. Therefore, the extract of Angelica sinensis could be used as an inhibitor of trichlorfon stress in fish.
... EQDM is reported to be a biphasic inducer of xenobiotic metabolism (Ørnsrud et al., 2011), and may be biotransformed by liver microsomal enzymes (CYPs) through a series of redox reactions, which generates ROS (Guengerich, 2006;Klotz and Steinbrenner, 2017). In agreement with a previous study on the effects of EQ in mouse liver (Kim, 1991), EQDM exposure was found to increase levels of reduced liver glutathione (GSH; Fig. 4 and Table 3). A dose-dependent increase in oxidized glutathione levels (GSSG) in livers of mice exposed to EQDM at doses above EQDM 3, indicated perturbation of liver redox homeostasis. ...
Article
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The use of the synthetic antioxidant ethoxyquin (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; EQ) in animal feed results in the presence of EQ residues and metabolites, including the EQ dimer (1,8′-bi(6-ethoxy-2,2,4- trimethyl-1,2-dihydroquinoline); EQDM) in animal food products. To investigate the toxicity and dose-response of dietary exposure to EQDM, male BALB/c mice were exposed to one of six dietary doses of EQDM, ranging from 0.015 to 518 mg/kg body weight/day for 90 days. Doses above 10 mg/kg body weight/day affected whole body lipid metabolism resulting in increased liver weights and decreased adipose tissue mass. Metabolomic screening of livers revealed alterations indicating incomplete fatty acid β-oxidation and hepatic oxidative stress. Histopathological evaluation and biochemical analyses of the liver confirmed the development of microvesicular steatosis and activation of the glutathione system. Hepatic protein profiling and pathway analyses suggested that EQDM-induced responses are mediated through activation of CAR/PXR nuclear receptors and induction of a NRF2-mediated oxidative stress response. Based on the development of microvesicular steatosis as the critical endpoint, a Reference Point for dietary EQDM exposure was established at 1.1 mg/kg body weight/day (BMDL10) from benchmark dose modelling. Applying an uncertainty factor of 200, an Acceptable Daily Intake of 0.006 mg EQDM/kg body weight was proposed.
... Some of them may be not related to EQ at all. Metabolism of EQ is not completely described neither in mammalian or fish, most likely due to methodological limitations in identification and quantification (Skaare and Nafstad, 1979;Sanders et al., 1996;Burka et al., 1996;Kim, 1991;He and Ackman, 2000b) of metabolites (Skaare and Roald, 1977;Skaare, 1979;Skaare and Nafstad, 1979;Skaare and Solheim, 1979;Sanders et al., 1996) many of which are highly reactive (Taimr et al., 1991;Thorrisson et al., 1992). In the present study, 4 of 14 observed compounds (Bohne et al., 2007a) were identified as parent EQ; de-ethylated EQ, earlier identified as a rat major urine metabolite (Skaare and Solheim, 1979); quinone imine, suspected product of in vitro oxidation of de-ethylated EQ (Skaare and Solheim, 1979), also found in salmonids (He and Ackman, 2000b); and finally, EQDM found in salmonids (He and Ackman, 2000b). ...
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The biological fate of the fish feed additive, ethoxyquin (EQ) was examined in the muscle of Atlantic salmon during 12 weeks of feeding followed by a 2 weeks depuration period. Parent EQ (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline), quinone imine (2,6-dihydro-2,2,4-trimethyl-6-quinolone), de-ethylated EQ (6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline) and EQDM (EQ dimer or 1,8'-di(1,2-dihydro-6-ethoxy-2,2,4-trimethyl-quinoline) were found to be the ubiquitous metabolites of dietary EQ, with EQDM as a main metabolite. A rapid decrease in the level of EQ (2.4 days of half-life) was balanced by an increase in EQDM, giving an unchanged net sum following 2 weeks of depuration. The mandatory 14 days depuration period prior to slaughtering of farmed salmon in Norway was not sufficient for complete elimination of EQ-derived residuals. Post depuration, EQDM accounted for 99% of sum of the two compounds in all treatment groups; possible toxicological effects of EQDM are not known. The individual concentrations of EQ and EQDM and their sum are dependent on EQ level in the feed, consequently, their residual concentrations may be controlled. The theoretical amount of EQ and EQDM consumed in one meal of farmed salmon would be under the recommended ADI, provided that the fish were raised on feed with no more than 150 mg EQ/kg feed, which is the EU maximum limit for EQ in fish feed.
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Publisher Summary This chapter describes the isolation of liver or kidney mitochondria. The selected tissue is disrupted by homogenization in cold isotonic sucrose. Differential centrifugation is then employed to separate the mitochondria from cell debris, red blood cells, nuclei, microsomes, and soluble components. For the isolation of liver mitochondria, the homogenate is distributed into Lusteroid centrifuge cups and centrifuged at 600 g for 10 minutes. The supernatant fraction is decanted and saved. The pellets may be dispersed by using the side of a stirring rod against the wall of the cup or by handoperating the homogenizer. The resuspended material is centrifuged at 600 g for 10 minutes. The supernatant fractions are combined. The pellets are discarded. This washing contributes not only to the yield of the final mitochondrial preparation, but also to its integrity, apparently by permitting the recovery of the larger mitochondria. For the isolation of kidney, the kidney capsule is removed by gently squeezing the kidney through the thumb and forefinger. The kidney is then cut sagittally. The medullary portion is removed and discarded. Mitochondria are then prepared from the cortex following the method described for liver, with the exception that the mitochondrial pellet need be washed only once. Method for testing the quality of mitochondria is also discusses in the chapter.
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Adult male rats were given the antioxidant 14C-ethoxyquin by oral intubation and were sacrificed at various time intervals from 0.5 hr to 6 days following administration of the drug. The distribution pattern was studied by whole-body autoradiography and liquid scintillation counting. The isotopelabelled antioxidant was distributed throoughout most tissues and the blood at 0.5 hr after administration. The highest radioactivity throughout the experimental period was observed in the liver, the kidney, the gastrointestinal tract and the adipose tissue. No activity was observed in the brain and the central nervous system. Of the dose ingested 2.2 and 0.2% were found in the liver at 0.5 hr and 6 days respectively following dosing. The hepatic peak in radioactivity was measured at 8 hrs and after 6 days 7.5% of this level was still present in the liver. Six days after administration residues of ethoxyquin and metabolites were also present in the kidney cortex, the intestines, the lung, various adipose tissue and blood.
Article
1. Biliary excretion and metabolites of ethoxyquin, and gastro-intestinal absorption of ethoxyquin were studied in rat. 2. An average of 28 and 36% of the dose of 14C following intragastric administration of [14C]ethoxyquin was recovered in the bile of bile-duct cannulated rats in 12 and 24 h, respectively. 3. By g.l.c.-mass spectrometry, 75 to 85% of the 14C excreted in the 12 h bile was identified as unchanged ethoxyquin, and the following metabolites were isolated and identified: 8-hydroxy-ethoxyquin, hydroxylated 8-hydroxy-ethoxyquin, 6-ethoxy-2,2,4-trimethyl-8-quinolone, hydroxylated 6-ethoxy-2,2,4-trimethyl-8-quinolone, 6-ethoxy-2,4-dimethylquinoline and 2,2,4-trimethyl-6-quinolone. 4. Three groups of rats were used in the biliary excretion experiments, and the effect of standardization of experimental conditions was demonstrated. Infusion of sodium taurocholate following bile-duct cannulation did not affect the biliary excretion kinetics of ethoxyquin. 5. Only about 3% of the radioactivity administered was absorbed from the gastrointestinal tract via the lymphatic pathway in thoracic-duct connulated rats within 24 h. It was concluded that ethoxyquin was absorbed primarily by the portal route.
Article
1. The metabolism of ethoxyquin (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline) in rat has been investigated. Urinary metabolites were identified by combined g.l.c.-mass spectrometry. 2. The major metabolic reaction was de-ethylation which gave rise to 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline and an oxidation product, 2,2,4-trimethyl-6-quinolone. Other reactions were hydroxylation to four different hydroxylated metabolites and one dihydroxylated metabolite. A total of 95% of the dose (100 mg/kg) was accounted for.
Article
A procedure is described for the estimation of the antioxidant ethoxyquin in feed and food products. It involves homogenization of the samples, extraction with methanol, and extraction of the antioxidant from the extract using n-hexane. Gas-liquid chromatography (GLC) with a flame ionization detector is used for quantitative determination, and GLC combined with mass spectrometry (MS) is applied for the confirmation of identity. Only the oxidation inhibitor 6-ethoxy-l,2-dihydro-2,2,4-trimethylquinoline (EMQ), which has not been involved in the antioxidative processes, is determined gas chromatographically. Recovery studies adding ethoxyquin at levels of 100 ppm to fish meal, fish meat, and broiler meat showed that about 30% of the GLC measurable antioxidant was recovered, whereas approximately 70% was recovered from water.
Article
The stability of 6-ethoxy-l,2-dihydro-2,2,4-trimethylquinoline (ethoxyquin, EMQ) was studied in n-hexane and chloroform with emphasis on the color changes of the solutions and the quantitative changes during 1 month of storage in the absence of light. Visual observations, gas-liquid chromatography (GLC), and GLC combined with mass spectrometry (MS) were used as the methods of analysis. The antioxidant was found to be extremely labile on exposure to light, and in chloroform solutions an increase of color intensity was observed together with a 35-70% loss of GLC measurable EMQ, the tenfold dilute solutions (0.1 mg/ml) being the least stable. The ethoxyquin dissolved in n-hexane, however, was found to remain unchanged even after the storage period. In conclusion, n-hexane is therefore recommended as the solvent for use in analytical work and for extractions from biological systems containing ethoxyquin. GLC using a 3% SE-30 column operated at 160° has been found to be suitable for quantization of EMQ when residues are to be determined in food products for example. The mass spectra of the GLC peaks were examined for characteristic fragmentation patterns.
Article
1. The toxic plant sesquiterpene lactones, helenalin, hymenoxon, mexicanin-E, tenulin, dihydrogriesenin, and psilotropin which were isolated from Helenium, Hymenoxys, and Geigeria spp markedly inhibited "state 3" respiration in mouse hepatic mitochondria. With the exception of dihydrogriesenin and psilotropin, all the other sesquiterpene lactones stimulated "state 4" respiration. 2. The sesquiterpene lactones also stimulated ATPase activity in the presence of Mg2+ ions and caused mitochondrial swelling in buffer solutions containing magnesium, sodium, ammonium and potassium chloride salts. 3. The number of alkylating sites present in a sesquiterpene lactone appears to be related to the inhibitory activity on mitochondrial oxidative phosphorylation, however, the structure-activity relationship of these lactones is not clear at present. 4. Mitochondria prepared from the liver of ethoxyquin hydrochloride-fed mice were less susceptible to sesquiterpene lactone-mediated inhibition of mitochondrial oxidative phosphorylation.
Article
1. Constitutive and ethoxyquin hydrochloride (EQ-HCl)-induced hepatic glutathione (GSH) S-transferase, GSH reductase, and GSH peroxidase activities were determined in 5 strains of 8-10 week old inbred male mice. 2. The constitutive GSH S-transferase (GST) activity varied from 2.9 (SJL/JCR) to 8.9 (C57BL/6NCR) mumol product formed/min/mg protein and the corresponding values for the EQ-HCl-treated mice were in the range of 15.3-25.3 mumol product formed/min/mg protein. 3. EQ-HCl induced GST activity in all the strains examined and this contrasted to the induction activity of Aroclor 1254 which was strain-dependent. GST activity was induced 2.9-fold in Aroclor 1254-responsive (C57BL/6) and 2.8-fold in non-responsive (DBA/2) mice, respectively.
Article
The effects of dietary administration of ethoxyquin (EQ) on aflatoxin B1 (AFB1) metabolism, DNA adduct formation and removal, and hepatic tumorigenesis were examined in male Fischer rats. Rats were fed a semipurified diet containing 0.4% EQ for 1 wk, gavaged with 250 micrograms of AFB1 per kg 5 times a wk during the next 2 wk, and, finally, restored to the control diet 1 wk after cessation of dosing. At 4 mo, focal areas of hepatocellular alteration were identified and quantitated by staining sections of liver for gamma-glutamyl transpeptidase. Treatment with EQ reduced by greater than 95% both area and volume of liver occupied by gamma-glutamyl transpeptidase-positive foci. Utilizing the same multiple dosing protocol, patterns of covalent modifications of DNA by AFB1 were determined. EQ produced a dramatic reduction in the binding of AFB1 to hepatic DNA: 18-fold initially and 3-fold at the end of the dosing period. Although binding was detectable at 3 and 4 mo postdosing, no effect of EQ was observed, suggesting that these persistent adducts are not of primary relevance to AFB1 carcinogenesis. Analysis of nucleic acid bases by high-performance liquid chromatography revealed no qualitative differences in adduct species between treatment groups. The inhibitory effect of EQ on AFB1 binding to DNA and tumorigenesis appears related to induction of detoxication enzymes. Rats fed 0.4% EQ for 7 days showed a 5-fold increase in hepatic cytosolic glutathione S-transferase (GST)-specific activities. Multiple molecular forms of GST were induced, and concomitant elevations in messenger RNA levels coding for the synthesis of GST subunits were observed. Correspondingly, biliary elimination of AFB1-glutathione conjugate was increased 4.5-fold in animals on the EQ diet during the first 2 h following p.o. administration of 250 micrograms of AFB1 per kg. Thus, induction by EQ of enzymes important to AFB1 detoxication, such as GST, can lead to enhanced carcinogen elimination, as well as reductions of AFB1-DNA adduct formation and subsequent expression of preneoplastic lesions, and, ultimately, neoplasia.
Article
We have studied the induction of rat liver gamma-glutamyl transpeptidase (GGT) mRNA by the antioxidant ethoxyquin and during aflatoxin B1-induced carcinogenesis. Using a rat kidney GGT cDNA probe, Northern blot analysis revealed that GGT mRNA induced in liver by either compounds was slightly larger than that found in untreated kidney. GGT mRNA was not detected in untreated liver or freshly isolated hepatocytes, but induction of the message in treated tissues correlated with the increase in enzymic activity observed by histochemistry and quantitative assay. Slot-blot analysis of poly(A)+ mRNA indicated that constitutive GGT mRNA levels in kidney were at least 5-fold greater than those in the most GGT-positive liver-derived tissue examined.
Article
Ethoxyquin (EQ, 1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline) was purified and converted to a crystalline, stable ethoxyquin hydrochloride (EQ-HCl). The readily available (technical grade) oily EQ reacted with concentrated hydrochloric acid (HCl) and precipitated as a crystalline salt (EQ-HCl) in acetone, leaving most of the impurities in solution. The regenerated free base (EQ) from the EQ-HCl was further purified by silicagel column chromatography to remove several minor contaminants, and the pure unstable EQ was immediately converted into a pure stable salt (EQ-HCl). The dietary administration of EQ-HCl, 0.25 or 0.5% in the feed, induced hepatic and intestinal thiols in mice and provided protection against toxic doses of pyrrolizidine alkaloids. The LD50 values of the 0.125 and 0.25% EQ-HCl-pretreated mice were 94.0 and 98.5 mg/kg, respectively, compared to that of controls, 71.3 mg/kg. The EQ-HCl-supplemented feed appeared to be more palatable, but other effects, such as the hepatic hypertrophy, the tissue thiol induction, and the protective effects, were comparable to those of unpurified EQ.
Article
Biological actions of 4 commonly used synthetic antioxidants--butylated hydroxyanisole, butylated hydroxytoluene, ethoxyquin and propyl gallate--on the molecular, cellular and organ level are complied. Such actions may be divided into modulation of growth, macromolecule synthesis and differentiation, modulation of immune response, interference with oxygen activation and miscellaneous. Moreover, an overview of beneficial and adverse interactions of these antioxidants with exogenous noxae is given. Beneficial interactions include radioprotection, protection against acute toxicity of chemicals, antimutagenic activity and antitumorigenic action. Possible mechanisms of the antitumorigenic action of antioxidants are discussed. This discussion is centered around antioxidant properties which may contribute to a modulation of initiation-related events, especially their ability to interfere with carcinogen metabolism. The beneficial interactions of antioxidants with physical and chemical noxae are contrasted to those leading to unfavorable effects. These include radiosensitization, increased toxicity of other chemicals, increased mutagen activity and increased tumor yield from chemical carcinogens. At present, the latter one can most adequately be characterized as tumor promotion at least in the case of butylated hydroxytoluene. It is concluded that current information is insufficient to promote expectations as to the use of antioxidants in the prevention of human cancer.
Article
Diets containing the antioxidant ethoxyquin (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline) were fed to female CD-1 mice for 10–38 days to assess their effects on monocrotaline toxicity, liver glutathione levels and hepatic drug metabolizing enzyme activities. Dietary ethoxyquin (0.25%) protected the mice against lethality as well as acute hepatotoxicity of monocrotaline as measured by the levels of alanine aminotransferase and asparate aminotransferase in plasma. Other feed additives with antioxidant properties such as vitamin C, vitamin E or selenium had no protective effect against monocrotaline lethality and hepatotoxicity. Dietary cysteine (1%) also protected mice against the lethality but not the acute hepatotoxicity of the alkaloid. With the exception of ethoxyquin, none of the other feed additives increased liver glutathione levels (mg/liver). Glutathione S-transferase activity was significantly increased by either dietary ethoxyquin or cysteine using chlorodinitrobenzene as substrate. Dietary ethoxyquin produced an increase in hepatic cytochrome P-450 content and an increase in the in vitro conversion of monocrotaline to pyrrole metabolites by liver microsomes. However, there was no effect of the feed additive on the activity of aminopyrine demethylase and on the concentration of pyrroles found in the liver 2 or 24 h after monocrotaline administration. Since ethoxyquin protected mice against monocrotaline lethality and hepatotoxicity despite no reduction in the in vivo activation of monocrotaline, the mechanisms involved are most probably a result of increased detoxication processes partly because of increased liver glutathione levels.
Article
Antidotal effects of the 2 antioxidants butylated hydroxyanisole (BHA) and ethoxyquin (EQ) were evaluated in bitterweed (Hymenoxys odorata DC) toxicosis in sheep. Bitteerweed contains a toxic sesquiterpene lactone, hymenoxon, the toxicity of which is reduced by cysteine. Both BHA and EQ are known to induce hepatic glutathione production in rodents. Treatment of sheep with EQ (2.5 g/sheep/day for 9 days before poisoning) gave significant protection from toxic doses of bitterweed, but the protective effect of BHA was insignificant. Of 6 sheep given EQ in the feed, 5 survived 7 doses of bitterweed (4 g/kg/day or higher for 7 days), whereas 5 of 7 controls and 4 of 7 sheep given feed with added BHA died. The added EQ in the feed decreased the serum alkaline phosphatase activity and total protein, albumin, and calcium concentrations. Seemingly, EQ is the first protective agent with field application potential for bitterweed toxicity.
Article
A diverse group of compounds inhibit the action of chemical carcinogens when administered prior to and/or simultaneously with the carcinogen. The inhibitors include naturally-occurring constituents of foods as well as synthetic compounds introduced into the environment. Three general mechanisms of inhibition exist. The first, illustrated by disulfiram inhibition of dimethylhydrazine-induced neoplasia of the large bowel, is the direct blocking of enzymatic activation of the carcinogen to its reactive ultimate carcinogenic form. The second mechanism of inhibition entails the stimulation of a coordinated detoxification response which results in increased activity of detoxifying enzymes in the microsomes and also the cytosol. At least two subdivisions of this response occur. One, for which butylated hydroxyanisole is a prototype, shows enhanced activity of some microsomal enzymes but not aryl hydrocarbon hydroxylase (AHH). However, it does have a rapidly active component which results in marked alteration of microsomal metabolism of benzo(a)pyrene. Another, for which a prototypical inhibitor is beta-naphthoflavone is characterized by induction of increased AHH activity. The third general mechanism of carcinogen inhibition entails the direct scavenging of reactive carcinogenic species by the inhibitor. Evidence supporting the psosibility that inhibitors play a role in the response of humans to carcinogens consists of three types. The first is the chemical diversity of the inhibitors and their actual occurrence in the environment. The second is the resposiveness of the detoxification systems, particularly those in the tissues of the major portals of entry, to the naturally-occurring or synthetic inhibitors. The third is a group of epidemiological studies which suggest that individuals consuming relatively large quantities of vegetables, a major source of naturally-occurring inhibitors, are at lower risk from gastrointestinal cancers.
  • Gornall A. G.