Iron intake affects lipid peroxidation and glutathione peroxidase activity of distal colonic mucosa

The purpose of this study was to examine the effect of low, adequate, and high dietary iron (Fe) levels on lipid peroxidation, glutathione S-transferase (GST) and glutathione peroxidase (GSH-Px) activities, and glutathione (GSH) concentrations in colon and liver. Male Sprague Dawley rats were fed iron deficient (DFe; 14 mg Fe/kg diet; N=8), adequate iron (AFe; 39 mg Fe/kg diet, N=8), or high iron (HFe; 454 mg Fe/kg diet; N=8) diets for 3 weeks. Liver Fe concentrations were 26, 84, and 243 ug/g wet weight, respectively, for rats fed DFe, AFe, and HFe diets (p<0.0001). Lipid peroxidation was increased 70% in distal colonic mucosa of rats fed HFe diets compared to that of rats fed AFe and DFe diets (p<0.01), but lipid peroxidation was unaffected by diet in proximal colon or liver. While distal colonic mucosal GSH-Px activity was lower in DFe rats (0.062 U/mg protein), than in AFe rats (0.091 U/mg protein), and HFe rats (0.089 U/mg protein) (p<0.05), iron intake had no effect on GSH-Px activity in proximal colon or liver. The distal colon had higher GSH-Px activity than proximal colon (p<0.0001). GST activity in colon and liver, and hepatic GSH concentrations were not altered by dietary iron intakes. This study suggests that distal and proximal colonic mucosa may respond differently to changes in Fe status.     

镧对小鼠肝脏氧化损伤及Cu、Zn、Mn、Fe含量的影响

目的研究稀土元素镧对雄性小鼠肝脏氧化损伤作用及对肝脏组织中微量元素含量的影响。方法雄性昆明小鼠40只,随机分为4组:阴性对照组和硝酸镧低(1mg/kg)、中(5mg/kg)、高(20mg/kg)剂量组,连续灌胃染毒2周后,测定肝脏组织中还原型谷胱甘肽(GSH)、丙二醛(MDA)含量和超氧化物歧化酶(SOD)活性。另取肝脏组织消化处理后,火焰原子吸收光谱法测定组织中铜(Cu)、锌(Zn)、锰(Mn)、铁(Fe)4种金属离子含量。结果硝酸镧染毒可明显降低雄性小鼠肝脏组织中GSH含量和SOD活性,提高MDA含量;小鼠肝脏组织微量元素测定结果显示:各剂量硝酸镧染毒组Cu、Zn含量明显降低,Fe含量有增加趋势,Mn含量与对照组比较差异无统计学意义。结论硝酸镧可造成雄性小鼠肝脏脂质过氧化损伤,这可能与镧干扰了Cu、Zn、Fe在肝脏内的分布和蓄积,进而抑制抗氧化酶活性,增强自由基活性有一定关系。     

Effects of metals and detergents on biotransformation and detoxification enzymes of leaping mullet (Liza saliens)

In this study, feral leaping mullet (Liza saliens) liver microsomal 7-ethoxyresorufin O-deethylase (EROD), and cytosolic glutathione S-transferases (GSTs) activities were investigated using 7-ethoxyresorufin, 1-chloro-2,4-dinitrobenzene (CDNB), and ethacrynic acid (EA) as substrates, respectively. The average EROD activity was found as 1139+/-175 pmol resorufin/min/mg protein. The average GST activities towards CDNB and EA were found as 1364+/-41 and 140+/-19 nmol/min/mg protein, respectively. We have, then, investigated the in vitro effects of some metals and detergents on CYP1A and GST activities in leaping mullet liver. Leaping mullet liver microsomal EROD activity was significantly inhibited by Hg (0.1 mM), Ni (0.1 mM), Cd (0.1 mM), Cu (0.1 mM), Zn (0.1 mM), Sb (0.1 mM), Fe2+ (1 mM), Co (1 mM), Al (1 mM), and Fe3+ (1 mM), with the percent inhibition of 80, 80, 77, 75, 70, 69, 56, 53, 46, and 44, respectively. Similarly, conjugation of CDNB catalyzed by GST was inhibited significantly to lesser extend by Hg (0.1mM), Sb (0.1 mM), Cd (0.1 mM), Cu (0.1 mM), Zn (0.1 mM), Fe3+ (1 mM), Co (1 mM), and Fe2+ (1 mM), with the percent inhibition of 70, 69, 65, 61, 54, 51, 47, and 43, respectively. The degrees of inhibition observed on GST catalyzed EA conjugation by Hg (0.1 mM), Cd (0.1 mM), Sb (0.1 mM), Cu (0.1 mM), and Zn (0.1 mM) were 86, 78, 69, 51, and 42, respectively. In addition to metals, the effect of various detergents on leaping mullet liver EROD, GST-CDNB, and GST-EA activities were studied. It was found that ionic detergents strongly inhibited the EROD activity, whereas much less inhibitions were observed with GST catalyzed activities. Therefore, the CYP1A inhibition potencies of metals and detergents suggest that their contribution to the overall CYP1A induction in polycyclic aromatic hydrocarbons contaminated environmental samples has to be taken into account for better interpretation of environmental studies.     

N—乙酰半胱氨酸对二甲基甲酰胺所致急性肝损伤的保护作用

目的 探讨N-乙酰半胱氨酸(NAC)对二甲基甲酰胺(DMF)所致急性肝损害的保护作用。方法 给小鼠腹腔注射一次1800mg/kg DMF后用NAC灌胃。测定血清山梨醇脱氢酶(SDH)、丙氨酰氨基转移酶(ALT)、甘胆酸(CG)、肝脏谷胱甘肽(GSH)、Na~ K~ -ATP酶、Ca~(2 )-ATP酶,观察肝脏病理改变。结果 与单纯染毒组比较,染毒后连续口服NAC组血清SDH、ALT、CG明显降低(P<0.05),肝脏GSH含量升高,Na~ K~ -ATP酶、Ca~(2 )-ATP酶活性增高(P<0.05),肝脏病理改变减轻。结论 NAC对DMF所致急性肝损伤有一定保护作用。     

Purification and characterization of aldehyde dehydrogenase from rat liver mitochondrial matrix

Aldehyde dehydrogenase (EC 1.2.1.3) has been purified to homogeneity from Sprague-Dawley rat liver mitochondrial matrix; its specific activity with propionaldehyde (1 mM at pH 9.0) is 1.4 mumol/min/mg. It has a native molecular weight of ca. 260,000 daltons, a subunit weight of 54,000 daltons and separates into two bands on isoelectric focusing (pI, 5.15 and 5.30); its extinction coefficient at 280 nm for 1 mg/ml solution is 1.2 and 280/260 nm ratio is 1.6. The enzyme prefers NAD over NADP as the coenzyme; the Km for NADP (67,000 microM) is three orders of magnitude greater than that for NAD (61 microM); the Km for acetaldehyde is 2 microM and for propionaldehyde is 0.8 microM at pH 7.0. The enzyme is reversibly inhibited by chloral (Ki = 3 microM) but is resistant to disulfiram inhibition. In addition another aldehyde dehydrogenase, first observed in the mitochondrial matrix during isoelectric focusing, has been partially purified. It has a Km for propionaldehyde of 0.7 mM and an isoelectric point of 6.4. Its activity with glutamic-gamma-semialdehyde (Km = 0.13 mM) is ca. 20 times higher than with propionaldehyde identifying the enzyme as glutamic-gamma-semialdehyde dehydrogenase (EC 1.5.1.12).     

Effect of cadmium on T4 outer ring monodeiodination by rat liver

The effect of cadmium on thyroxine (T4) outer ring monodeiodination was studied in vivo and in vitro in the rat liver. One microgram of T4 was incubated with rat liver homogenates in 50 mM Tris--HCl buffer, pH 7.4, with or without 0.5, 5, and 50 mM dithiothreitol (DTT) for 60 min in the presence of 10(-8) to 10(-3) M CdCl2, and the amount of 3,5,3'-triiodothyronine (T3) produced was determined by a specific radioimmunoassay. Subcutaneous injection of CdCl2, 1 mg/kg BW/day, 5 days a week for 10 weeks, to the rats resulted in a significant reduction in serum T3 concentration (by 37%) and hepatic T3 production from T4 (by 78 to 92%). In vitro addition of 1 microM to 1 mM CdCl2 to liver homogenates caused a concentration-dependent reduction in T3 generation. Without DTT a 50% reduction in the T4 to T3 converting activity was caused by 4 X 10(-6) M CdCl2. DTT (0.5 to 50 mM) partially restored T3 generation roughly in a concentration-dependent manner. These results indicate that cadmium has some effects on the metabolism of thyroid hormone.     

Optimization and application of glutamate cysteine ligase measurement in wildlife species

Glutamate cysteine ligase (GCL), synthesizing gamma-glutamylcysteine from glutamate and cysteine, is the rate-limiting enzyme in glutathione (GSH) biosynthesis. GCL activity measurement was optimized in tissues from deer mice, Sprague Dawley rats, and mallard ducks. Varying glutamic acid concentrations from 5 to 80 mM did not affect GCL activities markedly, whereas cysteine concentrations from 2.5 to 40 mM influenced GCL activities substantially. Optimal cysteine concentrations for deer mouse, Sprague Dawley rat, and mallard duck (respectively) were 30, 30, and 20 mM in liver, 10, 10, and 20 mM in kidney, 20, 20, and 30 mM in brain, and 30 mM in heart for all three species. Responses of mallard duck GCL activity to acid metalliferous water were evaluated. After subacute exposure, low doses increased GCL activity and GSH content in liver by 48.3% and 54.4%, respectively. High doses reduced GCL activities significantly in liver and kidney to 31.2% and 43.0% of the control, respectively.     

The effects of some divalent metals on cardiac and branchial Ca2+-ATPase in a freshwater fish Saccobranchus fossilis

The heart and gill of a freshwater fish Saccobranchus fossilis have been shown to contain a Ca2+-activated ATPase involved in Ca2+ transport. Enzyme showed optimal activity at 3 mM Ca2+ and 3 mM ATP for gills and at 3 mM Ca2+ and 1 mM ATP for heart. Mg2+ was equally effective in stimulating enzyme activity but was not essential for hydrolysis. Maximum activity was found in heart ventricular muscles as compared to gills. Among all the metals tested Hg2+ was the most toxic (IC50, 0.75 and 0.85 microM for heart and gill, respectively) followed by Pb2+, Mn2+, and Cd2+. The inhibition was concentration dependent and reached almost 100% with each metal at the highest concentration. Stimulation of enzyme activity was observed at lower concentrations of Mn2+ and Cd2+ but not with Pb2+ and Hg2+. Stimulation was more pronounced with Mn2+ than with Cd2+ in both heart and gills. The results indicated that the inhibitory effect of these metals might be through the Ca2+-ATPase which is a manifestation of the calcium pump in various tissues.     

Enhancement of glutathione and g-glutamylcysteine synthetase,the rate limiting enzyme of glutathione synthesis,by chemoprotective plant-derived food and beverage components in the human hepatoma cell line HepG2

Glutathione (GSH) is an important antioxidant and cofactor of detoxifying metabolism. Therefore, elevation of GSH as achieved by inducing g-glutamylcysteine synthetase (GCS), the limiting enzyme of GSH synthesis, may contribute to chemoprevention against cancer. In previous animal studies, increases in GCS were mainly found in liver and other organs that are not easily accessible in humans. Thus, employment and evaluation of alternative systems such as human-derived cell lines are encouraged. In the present experiment, we used the hepatoma cell line HepG2 to investigate the response of GCS and GSH to five plant-derived chemoprotectants contained in regularly consumed foodstuffs and beverages (kahweol/cafestol [K/C] [15.5-62.0 mM], a-angelicalactone [100-400 mM], benzyl isothiocyanate [1.7-5.0 mM], diallyl sulfide [175-700 mM], and quercetin [10-50 mM]). All treatments led to dose-dependent increases in both GCS activity and GSH concentration. Time course studies with K/C indicated that the enhancement of GCS preceded that of GSH, suggesting a causal relationship. K/C did not enhance g-glutamyl transpeptidase, a further enzyme that assists GSH-related chemoprotection. Although GCS induction has been suggested to require an initial short-lived GSH depletion, we did not find any decrease in GSH after 3 h of incubation with K/C. In summary, HepG2 cells were shown to be a useful model to investigate the capacity of potential chemoprotectants to enhance GCS and GSH. To our knowledge, the present study is also the first to show increases in GCS by K/C and a-angelicalactone in vitro and by diallyl sulfide and quercetin in any system.     

葡萄籽提取物的体外抗脂质过氧化作用

以大鼠肝、脑组织匀浆为材料研究葡萄籽提取物 (GSE)的抗氧化作用。组织匀浆与GSE共浴后 ,比色法测定丙二醛 (MDA)生成量。组织匀浆与GSE共浴后 ,分别以自由基诱导剂CCl4、H2 O2 和铁离子 -抗坏血酸 (Fe2 + VC)激发脂质过氧化作用 ,以MDA产生和还原型谷胱甘肽 (GSH)耗竭作为脂质过氧化作用程度指标。结果表明 ,GSE可明显降低大鼠肝、脑组织自发性MDA的生成 ,减轻CCl4、H2 O2 、Fe2 + VC所致的肝脏脂质过氧化反应 ,减轻肝组织GSH耗竭。提示GSE具有良好的抗脂质过氧化作用。     

The effect of carbaryl and malathion in combination on γ-glutamyl transpeptidase and glutathione S-alkyltransferase activityin vitro

Exposure to pesticides is a serious environmental problem, since a realm of uncertainty exists concerning the toxic effects on man. Due to economical and more efficacious reasons, pesticides are being used in combination. The use of pesticides in combination, especially carbaryl and malathion, has become increasingly prevalent in recent years. Carbaryl and maiathion in combination are known to distribute to the rat liver and kidney to a greater extent than when exposure is limited to either pesticide alone. Since, carbaryl or malathion as individual pesticides are known to react with glutathione (GSH) during their metabolism and alterations in rat blood and liver GSH content after subacute exposure to this combination were noted in earlier work from this laboratory, it is important to examine the glutathione related parameters in the rat liver and kidneyin vitro.Concentrations of 2 and 4 mM carbaryl and/or malathion were incubated with rat whole blood, liver and kidney homogenate and 10,000 × g supernatant to observe the effect of blood and liver glutathione (GSH) content, liver glutathione S-alkyl-transferase (GSAT) activity and liver and kidney -glutamyl transpeptidase (GGTP) levels. Liver homogenate GSH content significantly decreased with the increase in exposure time to carbaryl and/ or malathion, while blood GSH levels remained un-changed. Exposure of the liver GSAT enzyme with malathion and carbaryl/malathion in combination produced a two-fold increase in the enzyme's activity. Kidney GGTP activity was inhibited by carbaryl and/or malathion, while the activity in the liver was without change.     

Glutathione protects heavy metal-induced inhibition of hepatic microsomal ethoxyresorufin O-deethylase activity in Dicentrarchus labrax L

The in vitro effects of chromium (Cr(VI)), copper (Cu²⁺), iron (Fe²⁺), mercury (Hg²⁺), and zinc (Zn²⁺) were assessed on liver microsomal ethoxyresorufin O-deethylase (EROD) activity from a sea bass (Dicentrarchus labrax L.) preexposed under laboratory conditions to 2.7 μM β-naphthoflavone. The reduced glutathione (GSH) protection potential against heavy metal effects was also studied. The heavy metal concentration ranges used for this study were as follows: 10 pM–5 mM Cr(VI), 10 pM–100 μM Cu²⁺, 10 pM–1 mM Fe²⁺, 10 pM–10 μM Hg²⁺, and 10 pM–100 μM Zn²⁺. Liver microsomal EROD activity was significantly inhibited after in vitro exposure to Cr(VI) (500 μM), Cu²⁺ (1 μM), Fe²⁺ (100 μM), Hg²⁺ (100 pM), and Zn²⁺ (10 μM). Heavy metals inhibitory effect on liver EROD activity was ordered as follows: Hg²⁺>Cu²⁺>Zn²⁺>Fe²⁺>Cr(VI). Protective effects against Hg²⁺ (1 and 10 μM), Cu²⁺ (1, 10, and 100 μM), and Zn²⁺ (10, 50, and 100 μM) were observed in the presence of 0.5 mM GSH by a decrease in liver microsomal EROD activity inhibition. However, 0.5 mM GSH did not protect liver microsomal EROD activity from Cr(VI), and Fe²⁺-induced inhibition. The effect of metal mixtures (Cu²⁺+Zn²⁺, Zn²⁺+Fe²⁺, Zn²⁺+Cr(VI), and Cr(VI)+Fe²⁺) (100 μM) on liver microsomal EROD activity was also assessed, revealing a synergistic interaction.     

Determination of aldehyde dehydrogenase isozyme activity in human liver

As acetaldehyde (Ac-CHO) has been implicated as a cause of alcoholic liver injury, accurate knowledge concerning changes in the Ac-CHO oxidizing system in human liver is essential for the understanding of the pathogenesis. However, an assay system for aldehyde dehydrogenase (ALDH: EC 1.2, 1.3) isozymes in human biological material has not yet been established. In the present study, the assay systems for human liver ALDH isozyme activity were analyzed. In human red blood cells, in which only one type of ALDH isozyme, high Km ALDH, is present, a maximum activity was observed at a substrate concentration of over 300 microM. In human liver of the usual type in which ALDH I (low Km isozyme) was not deficient, the activity reached a first plateau at 12 microM Ac-CHO after which the activity started to increase again at 20 microM Ac-CHO and continued to increase until 5.0 mM Ac-CHO. In the liver of the unusual type, which is deficient in low Km ALDH, activity was not detected at Ac-CHO concentrations lower than 10 microM. These results indicate that the optimum substrate concentrations for the determination of ALDH isozymes are 12 microM for low Km, 300 microM for high Km and over 1 mM for very high Km ALDH isozymes. The maximum activities of these three isozymes in the liver were obtained at a pH ranging between 9.0-9.5 and at an NAD concentration of over 500 microM. From these results, it is concluded that the assay system of Blair and Bodley is applicable for the determination of ALDH isozyme activity in human biological material with the exception of determining Km values.     

Effects of manganese on rat brain microsomal Mg2+-Na+-K+-ATPase: in vivo and in vitro studies

The effect of manganese on brain microsomal Mg2+-Na+K+-ATPase was examined both in vitro and in vivo. Daily intraperitoneal administration of MnCl2 . 4H2O (Mn2+, 6 mg/kg) to the rats for a period of 90 days produced 10% (P less than 0.05) inhibition in the activity of Mg2+-ATPase, and 72 and 63% increases in the contents of manganese and copper, respectively, in the microsomal fraction of brain. In in vitro studies, lower concentrations of Mn2+ activated while higher concentrations inhibited the activity of brain microsomal ATPase. Addition of equal concentrations of Mn2+ + Cu2+ (8 mM) in vitro produced 8% inhibition in the activity of Mg2+-ATPase and 83% inhibition in Na+-K+-ATPase. Free Cu2+ ions were able to antagonize the effect of Mn2+ on ATPase in vitro and inhibited the activity of Mg2+-Na+-K+-ATPase with more pronounced effect of Na+-K+-ATPase. The lack of change in the activity of Na+-K+-ATPase in the brain microsomes of rats administered manganese, in spite of a significant increase in copper, could not be explained. It is, however, evident that a manganese-induced elevation in brain copper was not responsible for initiating biochemical changes in manganese neurotoxicity.     

Synergism of ascorbic acid and glutathione in the reduction of hexavalent chromium in vitro

The reduction of 20 microM hexavalent chromium [chromium(VI)] in single-reductant solutions of 0.02-2 mM L-ascorbic acid (L-AsA) or 2 mM reduced glutathione (GSH), and in mixed solutions of 2 mM GSH containing L-AsA of the above-described concentrations was investigated at physiological pH (37 degrees C). The reduction of chromium(VI) in the L-AsA solutions of higher concentrations showed pseudo-first-order kinetics in a single phase with respect to chromium(VI). In the lower L-AsA concentrations, pseudo-first-order processes appeared only in an early stage of the reaction. The reduction in the GSH solution was characterized by a two-phase process. In the first phase, which appeared in very short duration, the reaction rate was much higher than that in the second, but resulted in a decrease of only 7% of the initial chromium(VI) level. The second phase showed the main process of the reduction. This indicated pseudo-first-order kinetics. The half-life values of chromium(VI) depended on the initial levels of the reductants and ranged from seconds to hours. The chromium(VI)-reducing ability of L-AsA was markedly higher than that of GSH. In the mixed solutions of L-AsA and GSH, synergistic effect on the reduction of chromium(VI) was observed, especially in earlier stages of the processes. The synergism was more conspicuous in the mixed solutions containing lower L-AsA levels. These results suggest that although AsA possesses higher reducing ability than GSH, their coexistence is of importance for the reduction of chromium(VI) in biological systems because of their synergism.     

Effects of chemoprotective agents on the metabolic activation of the carcinogenic arylamines PhIP and 4-aminobiphenyl in human and rat liver microsomes

Carcinogenic aromatic amines, including the heterocyclic amines, may pose a significant health risk to humans. To determine the potential for chemoprotective intervention against the carcinogenicity of these arylamines and to better understand their mechanism of action, a range of agents, most of them natural dietary constituents, was examined in vitro for their ability to modulate the N-hydroxylation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 4-aminobiphenyl (ABP), an initial step in their bioactivation. Experiments were conducted with rat and human liver microsomes. The agents (diallyl sulfide, indole-3-carbinol, alpha-angelicalactone, cafestol/kahweol palmitates, cafestol, kahweol, benzylisothiocyanate, genistin, formononetin, daidzin, equol, biochanin A, Oltipraz, tannic acid, quercetin, ethoxyquin, green tea, and black tea) comprised a variety of chemical classes that included sulfur-containing compounds, antioxidants, flavonoids, phytoestrogens, diterpenes, and polyphenols. Several of these agents, quercetin, ethoxyquin, and black tea, were found to strongly inhibit PhIP N-hydroxylation in rat liver microsomes, resulting in a nearly 85-90% decrease in activity at 100 microM or 0.2%. Tannic acid and green tea, in addition to these agents, were also strong inhibitors of ABP N-hydroxylation. In human liver microsomes, each of these agents was strongly inhibitory (approx 85-95% at 100 microM or 0.02%) of PhIP and ABP N-hydroxylation. Theaflavins and polyphenols were judged to be the primary inhibiting components in the teas, the theaflavins showing the most potent effect. These results demonstrate that chemoprotective agents can inhibit the bioactivation of carcinogenic arylamines, and this is likely to be one of the mechanisms of protection.     

谷胱甘肽及VitB6对CS2染毒大鼠的保护作用研究

目的：为探讨金属离子络合及ＶｉｔＢ６代谢障碍在二硫化碳（ＣＳ２）神经毒作用中的作用；方法：测定ＣＳ２染毒大鼠脑组织中微量元素铜的含量，并用ＶｉｔＢ６及谷胱甘肽（ＧＳＨ）进行干预。以ＳＤ雄性大鼠为中毒模型，检测不同浓度（０，３００，６００，１２００，２４００ｍｇ／ｍ３）染毒两个月后脑组织铜的含量；同时在高浓度（２４００ｍｇ／ｍ３）组给予两种干预药物：ＧＳＨ（１００ｍｇ／ｋｇ，腹腔注射，一次／日），ＶｉｔＢ６（灌胃，一次／日，０．４ｍｇ／日），观察对大鼠行为及酶活性的影响。结果：ＣＳ２染毒大鼠脑组织铜含量无明显改变；ＧＳＨ，ＶｉｔＢ６对ＣＳ２致运动协调能力障碍无明显改善，对反映学习记忆能力的指标（步下法）有改善作用；ＧＳＨ对Ｎａ＋－Ｋ＋－ＡＴＰ酶活性有升高作用。结论：ＣＳ２所致中枢神经系统与外周神经系统毒性在机制上可能有所不同。     

Effects of paraquat on Mg2+-ATPase activity in rat liver

Intraperitoneal injection of paraquat (70 mg/kg) elicited a significant decrease of 20% in activity of Mg²⁺-ATPase in hepatic mitochondria, which is always surrounded by a high concentration of oxygen, in rats. The decrease of mitochondrial Mg²⁺-ATPase activity was completely abolished by pretreatment with vitamin E, which is a scavenger of oxygen radicals. On the other hand, paraquat administration did not change the Mg²⁺-ATPase activity in endoplasmic reticulum, which exists in an anaerobic condition in living cells. When liver microsomes were incubated with 1 mM paraquat under aerobic conditions, the Mg²⁺-ATPase activity was decreased by 42%. The decrease of Mg²⁺-ATPase activity was completely eliminated by pretreatment with vitamin E. Furthermore, lipid peroxidation in microsomes was tremendously increased by the addition of 1 mM paraquat under aerobic conditions. The increase of lipid peroxidation was completely abolished by preadministration of vitamin E in rats. The results suggest that the inhibition of Mg²⁺-ATPase activity induced by paraquat may be mediated by active oxgen, which is produced by the reaction of paraquat radicals; molecular oxygen may be involved in the induction of hepatic cell injury.     

Effect of nutritional status and ozone exposure on some biomarkers of oxidative stress in rat brain regions

The aim of this study was to analyze the effect of nutritional condition and simulated exposure to ozone on Glutathione (GSH), the activity of Na+/K+ ATPase and lipid peroxidation in rat brain. Male Wistar rats were fed with 7% and 23% protein diets. Two groups were formed for each nutritional condition: one group was exposed for 15 successive days to 0.75 ppm of ozone and the other to air. Subsequently, the brain was dissected in cortex, hemispheres, cerebellum, and brainstem to measure the activity of thiobarbituric acid reactive substances (TBARS), ATPase, and levels of GSH. The activity of Na+/K+ ATPase increased in cerebellum of well-nourished rats exposed to ozone, while total ATPase and TBARS decreased in all studied areas in the malnourished groups. The levels of GSH decreased significantly (P < 0.05) in the brain of rats fed with 7% of protein diet and exposed to ozone but increased in rats fed with normal diet and exposed to ozone. These results suggest that malnutrition causes alterations in the values of Na+/K+ ATPase, total ATPase, GSH, and lipid peroxidation, while ozone contributes to these modifications. As a consequence, both variables are involved in oxidative stress in the rat brain.     

Estrogenic activity of styrene oligomers after metabolic activation by rat liver microsomes

In this study we examined estrogenic activity of styrene oligomers after metabolic activation by rat liver microsomes. Trans-1,2-diphenylcyclobutane (TCB), cis-1,2-diphenylcyclobutane (CCB), 1,3-diphenylpropane, 2,4-diphenyl-1-butene, 2,4,6-triphenyl-1-hexene, and 1-alpha-phenyl-4ss-(1 -phenylethyl)tetralin were negative in the yeast estrogen screening assay and estrogen reporter assay using estrogen-responsive human breast cancer cell line MCF-7. However, TCB exhibited estrogenic activity after incubation with liver microsomes of phenobarbital-treated rats in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH). Minor activity was observed when liver microsomes of untreated or 3-methylcholanthrene-treated rats were used instead of those from phenobarbital-treated rats. CCB, 1,3-diphenylpropane, and 2,4-diphenyl-1-butene also exhibited estrogenic activity after metabolic activation by liver microsomes, but the activity was lower than that of TCB. 2,4,6-Triphenyl-1-hexene and 1-alpha-phenyl-4ss-(1 -phenylethyl)tetralin did not show estrogenic activity after such incubation. When TCB was incubated with liver microsomes of phenobarbital-treated rats in the presence of NADPH, three metabolites were detected by high-performance liquid chromatography (HPLC). One metabolite isolated by HPLC exhibited a significant estrogenic activity. The active metabolite was identified as trans-1-(4-hydroxyphenyl)-2-phenylcyclobutane by mass and nuclear magnetic resonance spectral analysis. These results suggest that the estrogenic activity of TCB was caused by the formation of the 4-hydroxylated metabolite.