Antioxidant Enzymes of Larvae of the Cabbage Looper Moth,Trzchoplusza Ni: Subcellular Distribution and Activities of Superoxide Dismutase,Catalase and Glutathione Reductase

In the mid-fifth instar larvae of the cabbage looper moth, Trichoplusia ni, the subcellular distribution of total superoxide dismutase was as follows: 3.05 units (70.0%), 0.97 units (22.3%), and 0.33 units (7.6%) mg^?1 protein in the mitochondrial, cytosolic and nuclear fractions, respectively. No superoxide dismutase activity was detected in the microsomal fraction. Catalase activity was unusually high and as follows: 283.4 units (47.3%), 150.1 units (25.1%). 142.3 units (23.8%), and 22.9 units (3.8%) mg^?1 protein in the mitochondrial, cytosolic, microsomal (containing peroxisomes), and nuclear fractions. No glutathione peroxidase activity was found, but appreciable glutathione reductase activity was detected with broad subcellular distribution as follows: 3.86 units (36.1%), 3.68 units (34.0%). 2.46 units (23.0%). and 0.70 units (6.5%) mg^?1 protein in the nuclear, mitochondrial, and cytosolic fractions, respectively. The unusually wide intracellular distribution of catalase in this phytophagous insect is apparently an evolutionary adaptation to the absence of glutathione peroxidase; hence, lack of a glutathione peroxidase-glutathione reductase role in alleviating stress from lipid peroxidation. Catalase working sequentially to superoxide dismutase, may nearly completely prevent the formation of the lipid peroxidizing OH radical from all intracellular compartments by the destruction of H₂O₂ which together with O^?₂ is a precursor of OH.     

Subcellular distribution and activities of superoxide dismutase,catalase, glutathione peroxidase,and glutathione reductase in the southern armyworm,Spodoptera eridania

In mid-fifth-instar larvae of the southern armyworm, Spodoptera eridania, the subcellular distribution of four antioxidant enzymes—superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPOX), and glutathione reductase (GR)—were examined. Two-thirds (4.26 units ·mg protein^?1) of the SOD activity was found in the cytosol, and one-thirds (2.13 units ·mg protein^?1) in the mitochondria. CAT activity was unusually high and not restricted to the microsomal fraction where peroxisomes are usually isolated. The activity was distributed as follows: cytosol (163 units) mitochondria (125 units) and microsomes (119 units). Similar to CAT, the subcellular compartmentalization of both GPOX and GR was unusual. No activity was detected in the cytosol, but in mitochondria and microsomes, GR levels were 5.49 and 3.09 units. Although GPOX activity exhibited 14–16-fold enrichment in mitochondria and microsomes, respectively, over the 850g crude homogenate, the level was negligible (mitochondria = 1.4 × 10^?3 units; microsomes = 1.6 × 10^?3 units), indicating that this enzyme is absent. The unusual distribution of CAT has apparently evolved as an evolutionary answer to the absence of GR from the cytosol, and the lack of GPOX activity.     

Subcellular distribution and properties of carbonyl reductase in guinea pig lung

On subcellular fractionation, carbonyl reductase (EC 1.1.1.184) activity in guinea pig lung was found in the mitochondrial, microsomal, and cytosolic fractions; the specific activity in the mitochondrial fraction was more than five times higher than those in the microsomal and cytosolic fractions. Further separation of the mitochondrial fraction on a sucrose gradient revealed that about half of the reductase activity is localized in mitochondria and one-third in a peroxidase-rich fraction. Although carbonyl reductase in both the mitochondrial and microsomal fractions was solubilized effectively by mixing with 1% Triton X-100 and 1 M KCl, the enzyme activity in the mitochondrial fraction was more highly enhanced by the solubilization than was that in the microsomal fraction. Carbonyl reductases were purified to homogeneity from the mitochondrial, microsomal, and cytosolic fractions. The three enzymes were almost identical in catalytic, structural, and immunological properties. Carbonyl reductase, synthesized in a rabbit reticulocyte lysate cell-free system, was apparently the same in molecular size as the subunit of the mature enzyme purified from cytosol. These results indicate that the same enzyme species is localized in the three different subcellular compartments of lung.     

Hepatic subcellular distribution of short-chain beta-ketoacyl coenzyme A reductase and trans-2-enoyl coenzyme A hydratase: 25- to 50-fold stimulation of microsomal activities by the peroxisome proliferator, di-(2-ethylhexyl)phthalate

The present study demonstrates unequivocally the existence of short-chain trans-2-enoyl coenzyme A (CoA) hydratase and beta-ketoacyl CoA reductase activities in the endoplasmic reticulum of rat liver. Subcellular fractionation indicated that all four fractions, namely, mitochondrial, peroxisomal, microsomal, and cytosolic contained significant hydratase activity when crotonyl CoA was employed as the substrate. In the untreated rat, based on marker enzymes and heat treatment, the hydratase activity, expressed as mumol/min/g liver, wet weight, in each fraction was: mitochondria, 684; peroxisomes, 108; microsomes, 36; and cytosol, 60. Following di-(2-ethylhexyl)phthalate (DEHP) treatment (2% (v/w) for 8 days), there was only a 20% increase in mitochondrial activity; in contrast, peroxisomal hydratase activity was stimulated 33-fold, while microsomal and cytosolic activities were enhanced 58- and 14-fold respectively. A portion of the cytosolic hydratase activity can be attributed to the component of the fatty acid synthase complex. Although more than 70% of the total hydratase activity was associated with the mitochondrial fraction in the untreated rat, DEHP treatment markedly altered this pattern; only 11% of the total hydratase activity was present in the mitochondrial fraction, while 49 and 29% resided in the peroxisomal and microsomal fractions, respectively. In addition, all four subcellular fractions contained the short-chain NADH-specific beta-ketoacyl CoA (acetoacetyl CoA) reductase activity. Again, in the untreated animal, reductase activity was predominant in the mitochondrial fraction; following DEHP treatment, there was marked stimulation in the peroxisomal, microsomal, and cytosolic fractions, while the activity in the mitochondrial fraction increased by only 39%. Hence, it can be concluded that both reductase and hydratase activities exist in the endoplasmic reticulum in addition to mitochondria, peroxisomes, and soluble cytoplasm.     

Scavenger Enzyme Activities in Subcellular Fractions of White Clover (Trifolium repens L.) under PEG-induced Water Stress

Scavenger enzyme activities in subcellular fractions under polyethylene glycol (PEG)-induced water stress in white clover (Trifolium repens L.) were studied. Water stress decreased ascorbic acid (AA) content and catalase (CAT) activity and increased the contents of hydrogen peroxide (H₂O₂), thiobarbituric acid reactive substances (TBARS) (measure of lipid peroxidation), and activities of superoxide dismutase (SOD), its various isozymes, ascorbate peroxidase (APOX), and glutathione reductase (GR) in cellular cytosol, chloroplasts, mitochondria, and peroxisomes of Trifolium repens leaves. In both the PEG-treated plants and the control, chloroplastic fractions showed the highest total SOD, APOX, and GR activities, followed by mitochondrial fractions in the case of total SOD and GR activities, whereas cytosolic fractions had the second greatest APOX activity. However, CAT activity was the highest in peroxisomes, followed by the cytosol, mitochondria, and chloroplasts in decreasing order. Although Mn-SOD activity was highest in mitochondrial fractions, residual activity was also observed in cytosolic fractions. Cu/Zn-SOD and Fe-SOD were observed in all subcellular fractions; however, the activities were the highest in chloroplastic fractions for both isoforms. Total Cu/Zn-SOD activity, the sum of activities observed in all fractions, was higher than other SOD isoforms. These results suggest that cytosolic and chloroplastic APOX, chloroplastic and mitochondrial GR, mitochondrial Mn-SOD, cytosolic and chloroplastic Cu/Zn-SOD, and chloroplastic Fe-SOD are the major scavenger enzymes, whereas cellular CAT may play a minor role in scavenging of O₂⁻ and H₂O₂ produced under PEG-induced water stress in Trifolium repens.     

Oxygen metabolism in rabbit bone marrow and liver.

Oxygen metabolism has been quantified in rabbit bone marrow and liver. NADPH-Cytochrome $\text{c}$ reductase activity in bone marrow microsomal and cytosol fractions was about 40% of that found in liver. Superoxide anion and peroxide generation were found to be present in both liver and bone marrow. Catalase and superoxide dismutase activity were measured in liver and in marrow preparations free of erythrocytes; while liver catalase activity was approximately twice that of bone marrow, very low superoxide dismutase activity was observed in erythrocyte free bone marrow homogenates.     

Extraction of corticosterone from cell homogenates and subcellular fractions of the rat adrenal cortex. III. ACTH-induced temporal subcellular redistributions of steroid precursors to corticosterone

Cholesterol, pregnenolone, progesterone, 11-deoxycorticosterone (11-DOC) and corticosterone were quantitated in subcellular fractions isolated from in vivo adrenocorticotropin (ACTH)-stimulated rat adrenal zona fasciculata/reticularis. Six adrenal subcellular fractions separated by discontinuous sucrose gradient centrifugation (lipid, 0.125 M sucrose, cytosolic, microsomal, mitochondrial and nuclear) were extracted with alkaline ether/ethanol and assayed by high pressure liquid chromatography (HPLC). Lipid fractions contained the major cholesterol stores, while most pregnenolone and progesterone was found in lipid, microsomal and mitochondrial fractions. The 0.125 M sucrose and cytosol fractions together contained approximately 75% of the total 11-DOC and corticosterone. The five steroids were only present in small amounts in organelle fractions containing steroidogenic enzymes. Homogenate and lipid fraction cholesterol decreased between 10 and 15 min and again 30 min after ACTH injection. In the homogenate, lipid, microsomal and mitochondrial fractions, pregnenolone and progesterone were increased after ACTH injection; peak pregnenolone and progesterone concentrations were often measured in adrenal gland sucrose, cytosolic, microsomal and mitochondrial fractions 15 to 20 min after rats were injected with ACTH. Although ACTH increased 11-DOC and corticosterone in all but the mitochondrial and nuclear fractions, the sucrose, cytosolic and microsomal 11-DOC, and cytosolic corticosterone increased most dramatically. In many fractions, peak 11-DOC and corticosterone concentrations were most often observed between the 10 and 15 min periods and again at 30 min.     

Glutathione dependent control of protein disulfide-sulfhydryl content by subcellular fractions of hepatic tissue

The disulfide-sulfhydryl (SS/SH) ratios of subcellular fractions of rat hepatic tissue were found to vary diurnally with the ratio lowest in the early morning and highest in the early evening. These changes were found in the nuclear, microsomal and cytosol fractions. The primary reaction is the reversible formation of mixed disulfides of glutathione with proteins. This formation is controlled by the activity of thiol transferase and the level of oxidized glutathione (GSSG) as substrate. Several enzymes including mitochondrial and microsomal oxidases, glutathione reductase and peroxidase and glucose-6-phosphate dehydrogenase were found to control the levels of GSSG. An NADPH-dependent microsomal oxidase system, inhibited by GSSG, was found to produce activated oxygen which served as substrate for flutathione peroxidase. Evidence is presented for the concept that the formation of mixed disulfides of proteins with glutathione is a mechanism for maintenance of a disulfide-sulfhydryl ratio such that the integrity of particulate membranes is maintaine during oxidative and reductive stresses on the hepatic cells.     

Oxidative stress in toadfish (Halobactrachus didactylus) cardiac muscle. Acute exposure to vanadate oligomers

Vanadate solutions as ‘metavanadate’ (containing ortho and metavanadate species) and ‘decavanadate’ (containing manly decameric species) (5 mM; 1 mg/kg) were injected intraperitoneously in Halobatrachus didactylus (toadfish), in order to evaluate the contribution of decameric vanadate species to vanadium (V) intoxication on the cardiac tissue. Following short-term exposure (1 and 7 days), different changes on antioxidant enzyme activities—superoxide dismutase (SOD), catalase (CAT), selenium-glutathione peroxidase (Se-GPx), total glutathione peroxidase (GPx), lipid peroxidation and subcellular vanadium distribution were observed in mitochondrial and cytosolic fractions of heart ventricle toadfish. After 1 day of vanadium intoxication, SOD, CAT and Se-GPx activities were decreased up to 25%, by both vanadate solutions, except mitochondrial CAT activity that increased (+23%) upon decavanadate administration. After 7 days of exposure, decavanadate versus metavanadate solutions promoted different effects mainly on cytosolic CAT activity (−56% versus −5%), mitochondrial CAT activity (−10% versus +10%) and total GPx activity (+1% versus −35%), whereas lipid peroxidation products were significantly increased (+82%) upon 500 μM decavanadate intoxication. Accumulation of vanadium in total (0.137±0.011 μg/g) and mitochondrial (0.022±0.001 μg/g) fractions was observed upon 7 days of metavanadate exposure, whereas for decavanadate, the concentration of vanadium increased in cytosolic (0.020±0.005 μg/g) and mitochondrial (0.021±0.009 μg/g) fractions. It is concluded that decameric vanadate species are responsible for a strong increase on lipid peroxidation and a decrease in cytosolic catalase activity thus contributing to oxidative stress responses upon vanadate intoxication, in the toadfish heart.     

Subcellular distribution and properties of aldehyde dehydrogenase from 2-acetylaminofluorine-induced rat hepatomas

The subcellular distribution and properties of four aldehyde dehydrogenase isoenzymes (I-IV) identified in 2-acetylaminofluorene-induced rat hepatomas and three aldehyde dehydrogenases (I-III) identified in normal rat liver are compared. In normal liver, mitochondria (50%) and microsomal fraction (27%) possess the majority of the aldehyde dehydrogenase, with cytosol possessing little, if any, activity. Isoenzymes I-III can be identified in both fractions and differ from each other on the basis of substrate and coenzyme specificity, substrate K(m), inhibition by disulfiram and anti-(hepatoma aldehyde dehydrogenase) sera, and/or isoelectric point. Hepatomas possess considerable cytosolic aldehyde dehydrogenase (20%), in addition to mitochondrial (23%) and microsomal (35%) activity. Although isoenzymes I-III are present in tumour mitochondrial and microsomal fractions, little isoenzyme I or II is found in cytosol. Of hepatoma cytosolic aldehyde dehydrogenase activity, 50% is a hepatoma-specific isoenzyme (IV), differing in several properties from isoenzymes I-III; the remainder of the tumour cytosolic activity is due to isoenzyme III (48%). The data indicate that the tumour-specific aldehyde dehydrogenase phenotype is explainable by qualitative and quantitative changes involving primarily cytosolic and microsomal aldehyde dehydrogenase. The qualitative change requires the derepression of a gene for an aldehyde dehydrogenase expressed in normal liver only after exposure to potentially harmful xenobiotics. The quantitative change involves both an increase in activity and a change in subcellular location of a basal normal-liver aldehyde dehydrogenase isoenzyme.     

Antioxidant status of the potato tuber and Ca2+ deficiency as a physiological stress

The antioxidant status of potato ( Solanum tuberosum L.) tubers of two genotypes, cv. Désirée and clone 10337de40 was investigated in relation to susceptibility to internal rust spot (IRS), a Ca²⁺-related physiological disorder. Concentrations of total calcium within the perimedulla tissue of tubers, grown with a restricted (1 m M CaCl₂) Ca²⁺ supply, were similar in cv. Désirée (IRS resistant) and clone 10337de40 (IRS susceptible). A range of antioxidants was assayed in order to assess antioxidant status in both genotypes under the two Ca²⁺ treatments. Although no appreciable differences were detected between low Ca²⁺ and control treatments, certain antioxidants were present at significantly higher levels in the IRS resistant genotype, cv. Désirée. These included dehydroascorbate reductase (EC 1.8.5.1) activity (more than 100% higher), total glutathione content (ca 40% higher), glutathione reductase (EC 1.6.4.2) activity (almost 50% higher), peroxidase (EC 1.11.1.7) activity (ca 60% higher) and superoxide dismutase (EC 1.15.1.1) activity (almost 80% higher). There was no difference in ascorbate content, ascorbate free radical reductase activity (EC 1.6.5.4), α-tocopherol levels and catalase activity (EC 1.11.1.6) between the two genotypes. The possible relationship between resistance to IRS and a superior antioxidant status, found in cv. Désirée, is discussed.     

Effect of Peroxynitrite on the Mitochondrial Respiratory Chain: Differential Susceptibility of Neurones and Astrocytes in Primary Culture

Abstract: The effect of the neurotoxic nitric oxide derivative, the peroxynitrite anion (ONOO⁻), on the activity of the mitochondrial respiratory chain complexes in cultured neurones and astrocytes was studied. A single exposure of the neurones to ONOO⁻ (initial concentrations of 0.01–2.0 m M ) caused, after a subsequent 24-h incubation, a dose-dependent decrease in succinate-cytochrome c reductase (60% at 0.5 m M ) and in cytochrome c oxidase (52% at 0.5 m M ) activities. NADH-ubiquinone-1 reductase was unaffected. In astrocytes, the activity of the mitochondrial complexes was not affected up to 2 m M ONOO⁻. Citrate synthase was unaffected in both cell types under all conditions studied. However, lactate dehydrogenase activity released to the culture medium was increased by ONOO⁻ in a dose-dependent manner (40% at 0.5 m M ONOO⁻) from the neurones but not from the astrocytes. Neuronal glutathione concentration decreased by 39% at 0.1 m M ONOO⁻, but astrocytic glutathione was not affected up to 2 m M ONOO⁻. In isolated brain mitochondria, only succinate-cytochrome c reductase activity was affected (22% decrease at 1 m M ONOO⁻). We conclude that the acute exposure of ONOO⁻ selectively damages neurones, whereas astrocytes remain unaffected. Intracellular glutathione appears to be an important factor for ameliorating ONOO⁻-mediated mitochondrial damage. This study supports the hypothesis that the neurotoxicity of nitric oxide is mediated through mitochondrial dysfunction.     

Relationship between active oxygen species and cardenolide production in cell cultures of Digitalis thapsi: effect of calcium restriction

Elimination of calcium ions from the medium of undifferentiated cell cultures of Digitalis thapsi increased cardenolide production and induced extracellular H₂O₂ accumulation, as measured by the quenching of pyranine fluorescence. The addition of catalase reduced the response and the inclusion of superoxide dismutase enhanced the loss of fluorescence. This suggested that, besides H₂O₂, the superoxide anion was also formed before dismutating to H₂O₂. Additionally, exogenous H₂O₂ or superoxide dismutase stimulated cardenolide production whereas the addition of catalase markedly reduced it. These results point to a connection between H₂O₂ and cardenolide formation. The absence of calcium did not alter the levels of lipid peroxidation products; however, changes in the antioxidant system of D. thapsi cells were observed. Catalase activity was extremely low in control cultures and remained unaltered upon calcium elimination. Ascorbate peroxidase activity was not modified in calcium-free cultures. By contrast, calcium deprivation stimulated superoxide dismutase activity and strongly inhibited glutathione reductase activity. Also, a significant decrease in reduced glutathione was observed. These responses were emulated by treatment of the cultures with the glutathione biosynthesis inhibitor buthionine sulfoximine and by ethyleneglycol-bis-β-aminoethyl ether and LaCl₃. All these results indicate that the depletion of extracellular calcium induces changes in the redox state of cells and suggest that this alteration stimulates cardenolide formation in D. thapsi cultures.     

Phosphatidylinositol kinase,phosphatidylinositol-4-phosphate kinase and diacylglycerol kinase activities in rat brain subcellular fractions

Subcellular fractions isolated and purified from rat brain cerebral cortices were assayed for phosphatidylinositol (PI-), phosphatidylinositol-4-phosphate (PIP-), and diacylglycerol (DG-) kinase activities in the presence of endogenous or exogenously added lipid substrates and [γ-³²P]ATP. Measurable amounts of all three kinase activities were observed in each subcellular fraction, including the cytosol. However, their subcellular profiles were uniquely distinct. In the absence of exogenous lipid substrates, PI-kinase specific activity was greatest in the microsomal and non-synaptic plasma membrane fractions (150–200 pmol/min per mg protein), whereas PIP-kinase was predominantly active in the synaptosomal fraction (136 pmol/min per mg protein). Based on percentage of total protein, total recovered PI-kinase activity was most abundant in the cytosolic, synaptosomal, microsomal and mitochondrial fractions (4–11 nmol/min). With the exception of the microsomal fraction, a similar profile was observed for PIP-kinase activity when assayed in the presence of exogenous PIP (4 nmol/20 mg protein in a final assay volume of 0.1 ml). Exogenous PIP (4 nmol/20 mg protein) inhibited PI-kinase activity in most fractions by 40–70%, while enhancing PIP-kinase activity. PI- and PIP-kinase activities were observed in the cytosolic fraction when assayed in the presence of exogenously added PI or PIP, respectively, but not in heat-inactivated membranes containing these substrates. When subcellular fractions were assayed for DG-kinase activity using heat-inactivated DG-enriched membranes as substrate, DG-kinase specific activity was predominantly present in the cytosol. However, incubation of subcellular fractions in the presence of deoxycholate resulted in a striking enhancement of DG-kinase activities in all membrane fractions. These findings demonstrate a bimodal distribution between particulate and soluble fractions of all three lipid kinases, with each exhibiting its own unique subcellular topography. The preferential expression of PIP-kinase specific activity in the synaptic membranes is suggestive of the involvement of PIP₂ in synaptic function, while the expression of PI-kinase specific activity in the microsomal fraction suggests additional, yet unknown, functions for PIP in these membranes.     

Properties of cytosolic components activating rat hepatic 5'' [corrected]-deiodination in the presence of NADPH.

The effects of cytosol, NADPH and reduced glutathione (GSH) on the activity of 5'-deiodinase were studied by using washed hepatic microsomes from normal fed rats. Cytosol alone had little stimulatory effect on the activation of microsomal 5'-deiodinase. NADPH had no stimulatory effect on the microsomal 5'-deiodinase unless cytosol was added. 5'-deiodinase activity was greatly enhanced by the simultaneous addition of NADPH and cytosol (P less than 0.001); this was significantly higher than that with either NADPH or cytosol alone (P less than 0.001). GSH was active in stimulating the enzyme activity in the absence of cytosol, but the activity of 5'-deiodinase with 62 microM-NADPH in the presence of cytosol was significantly higher than that with 250 microM-GSH in the presence of the same concentration of cytosol (P less than 0.001). The properties of the cytosolic components essential for the NADPH-dependent activation of microsomal 5'-deiodinase independent of a glutathione/glutathione reductase system were further assessed using Sephadex G-50 column chromatography to yield three cytosolic fractions (A, B and C), wherein A represents pooled fractions near the void volume, B pooled fractions of intermediate Mr (approx. 13 000), and C of low Mr (approx. 300) containing glutathione. In the presence of NADPH (1 mM), the 5'-deiodination rate by hepatic washed microsomes is greatly increased if both A and B are added and is a function of the concentrations of A, B, washed microsomes and NADPH. A is heat-labile, whereas B is heat-stable and non-dialysable. These observations provide the first evidence of an NADPH-dependent cytosolic reductase system not involving glutathione which stimulates microsomal 5'-deiodinase of normal rat liver. The present data are consistent with a deiodination mechanism involving mediation by a reductase (other than glutathione reductase) in fraction A of an NADPH-dependent reduction of a hydrogen acceptor in fraction B, followed by reduction of oxidized microsomal deiodinase by the reduced acceptor (component in fraction B).     

The subcellular distribution of beta-carotene in bovine corpus luteum

The distribution of beta-carotene was determined in various subcellular fractions of bovine corpus luteum. It was found in significant amounts in all subcellular fractions examined including nuclear, mitochondrial, microsomal, cytosolic, and floating lipid. Much of the beta-carotene found in the crude nuclear and mitochondrial fractions was loosely bound and could be removed with repeated washings. In contrast, the microsomal beta-carotene could only be removed by detergent extraction suggesting that it is an integral component of this membrane preparation. In the cytosol fraction beta-carotene was bound to high-molecular-weight protein(s), quite possibly a plasma-derived lipoprotein. The subcellular distribution of beta-carotene in corpus luteum is quite similar to the distribution of its metabolite, retinol, in liver. This finding coupled with other recently published data suggests that beta-carotene could play a distinct role in corpora lutea function.     

Developmental Aspects of Detoxifying Enzymes in Fish (Salmo Iridaeus)

The activities of superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, glutathione transferase and glyoxalase I have been studied during the embryologic development of rainbow trout (Salmo iridaeus) and in several other trout tissues to investigate the protective development metabolism.

A gradual increase of superoxide dismutase, catalase, glutathione reductase, glyoxalase I and glutathione transferase activities was noted throughout embryo development.

In all trout tissues investigated glutathione peroxidase was found to be extremely low compared to catalase activity. The highest activity of superoxide dismutase, glyoxalase I and glutathione reductase was found in liver followed by kidney.

No change in the number of GST subunits was noted with the transition from the embryonic to the adult stages of life according to the SDS/PAGE and HPLC analyses performed on the GSH-affinity purified fractions.     

外源一氧化氮提高白灵侧耳菌丝耐热性生化途径分析

为了探索外源一氧化氮（NO）提高食用菌菌丝体耐热性的生化途径,以白灵侧耳Pleurotus eryngii var. tuoliensis菌株CCMSSC 00489为材料,通过测定高温胁迫下外源添加硝普钠（sodium nitroprusside,SNP,NO供体）后,菌丝体内超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、谷胱甘肽还原酶（GR）和过氧化物酶（POD）等4个抗氧化酶活性的变化,研究外源NO在高温胁迫响应中对抗氧化酶的影响。试验表明,高温胁迫致使菌丝体内TBARS含量升高,膜脂过氧化加剧。在正常温度培养（CK）下,外源添加SNP无显著缓解膜脂过氧化的效果,而高温胁迫条件下缓解效果显著,高温胁迫6h和12h,TBARS含量较对照（未添加）分别下降31.5%和25%。研究表明,抗氧化酶类对外源NO的响应不同。在有外源添加SNP的高温胁迫条件下,菌丝体内的SOD、CAT和GR活性随处理时间的延长而显著增强,在处理72h达到最高,分别是对照（0h）的1.73、7.29和4.95倍。其中CAT是高温胁迫响应的主要抗氧化酶类,其活力可以mmol/L·min^-1·mg^-1 of protein计量,而其他种类的活力均仅以μmol/L·min^-1·mg^-1 of protein计量。在试验条件下,这些抗氧化酶类活性的提高与TBARS含量的降低相呼应,表明外源NO通过提高SOD、CAT、GR的活性降低高温胁迫下的活性氧水平,缓解其氧化损伤,提高菌丝体耐热性。POD活性在外源添加SNP的高温胁迫条件下显著降低。     

Acute Hexachlorocyclohexane-Induced Oxidative Stress in Rat Cerebral Hemisphere

Hexachlorocyclohexane (HCH) is reported to induce oxidative stress in liver and testis of rat. With an objective to examine its effect on brain tissue acute toxicity of HCH (10 and 20 mg/kg body wt, i.p.) on the antioxidant defense system of cerebral hemisphere of rat was evaluated. Lipid peroxidation (LPX) was elevated after 24 h in the crude homogenate and sub-cellular fractions (nuclear and mitochondrial) except the microsomal fraction in which LPX was induced after 6 h and remained elevated till 24 h. The pesticide elicited decrease in the activities of cytosolic total, CN^–-sensitive (not at 24 h) and CN-resistant superoxide dismutases; total, Se-dependent and Se-independent glutathione peroxidases; and catalase throughout the measurement period. In contrast, glutathione reductase activity was elevated till 24 h after a fall at 6 h of pesticide exposure. Cerebral contents of glutathione and ascorbic acid were decreased in response to HCH. The results suggest the possible involvement of reactive oxygen species in the mechanism of HCH-induced neurotoxicity in rat.