SH Compounds Research Articles

Uji Kadar Albumin dan Pertumbuhan Ikan Gabus (Channa striata) dengan Kadar Protein Pakan Komersial yang Berbeda <Br><I>[Albumin Level Test and Snakehead Fish (Channa striata) Growth with Different Commercial Feed Protein Level]<I>

Abstract Gabus fish is rich of albumin. This fish as albumin source for hypoalbumin (lower albumin) patients and wound, both post operation wound and burn. Albumin have many sulfhydrile compound (SH) have a function as radikal bind. Protein which have rich of –SH compound be able to binding hazard metal and also antioxidant effects and salic acid. At present, albumin produced from human blood, then the price is expensive enough. The finding of albumin extract from gabus fish then become alternative to get cheap albumin. This research purposed to recognize about the influence by providing different protein feed on albumin level and the growth of gabus fish. Method that used in this research is experimental method, with Complete Random Design as trial design. Treatment that given such different protein level included, Po treatment with 26% protein, P1 treatment with 29% protein, P2 treatment with 32% protein respective repeated six times. The main parameter that observed are albumin and growth of Gabus fish. Supporting parameter that observed in this research are temperature measurement, pH and DO, Variant Analysis (ANOVA) and to know about Duncan Multiple Range test treatment. The result of the research indicates that found different albumin level on Gabus fish is not real among treatment above on observation yields. The highest average of albumin level found in P2 treatment, while lowest influence taken from treatments of P0 and P1. The growth of Gabus fish with providing commercial feed with different protein level indicates that found different growth of real Gabus fish (p< 0,05). The highest yield taken from P2 treatment is really different with other treatments. While lowest yield taken from P0 and P2 treatment.

Possible chemical forms of cadmium and varietal differences in cadmium concentrations in the phloem sap of rice plants (Oryza sativa L.)

In rice (Oryza sativa L.), cadmium (Cd), a toxic heavy metal, is found in phloem sap and eventually accumulates in the grains. To further characterize phloem-transported Cd, the chemical forms of Cd and other metals and varietal differences in phloem sap Cd concentrations were investigated in young rice plants. The size-exclusion chromatography elution times for Cd-bound compounds indicated that phloem Cd in cv. Nipponbare exists mainly as an approximately 13 kDa complex. Protease digestion of rice phloem sap reduced the bound Cd content from 92 to 19%. The remaining Cd may bind to low-molecule SH compounds. An experiment examining in vitro addition of Cd2+ to phloem sap from non-Cd-treated plants revealed that rice phloem sap constitutively contains Cd chelators. The major Cd peak is distinguishable from those of Fe, Zn, Cu, Mn, Ni and Co, which probably bind to nicotianamine, 2′-deoxymugineic acid, citrate and histidine. The Cd concentrations of the phloem saps in three varieties (Milyang 23, LAC 23 and Koshihikari) grown under the same soil conditions were correlated with their grain Cd concentrations, which had been reported previously, whereas the concentrations of the xylem saps were not. In conclusion, rice phloem sap Cd differs from other metals as it may bind to a novel approximately 13 kDa protein and SH compounds, and the concentration of Cd in rice phloem sap may be a key determinant of its grain content.

Nitrogen assimilation and cysteine biosynthesis in barley: Evidence for root sulphur assimilation upon recovery from N deprivation

The mixed effects of nitrogen nutrition and sulphate assimilation were investigated in barley plants (Hordeum vulgare var. Alfeo) that were subjected to long-term sulphur and/or nitrogen starvation, by measuring the O-acetylserine(thio)lyase (OASTL–EC 4.2.99.8) activity, changes in –SH compounds and amino acid levels.The growth of barley plants cultured in the hydroponic vessels was severely affected by altered nutrient levels. The barley plants grown in medium deprived of nitrogen and/or sulphur sources for 21 days showed increase in both root length and weight. In contrast, the shoot growth was reduced in nitrogen-starved plants and was unaffected by sulphur deprivation. Sulphur starvation affected the level of proteins in barley plants more than nitrogen deprivation. The decline in the protein levels observed under sulphur-deficient conditions was coupled with the accumulation of glutamine, asparagine and serine, mainly in the roots; additionally, a nitrogen deficiency in the roots promoted a decrease in both glutathione and cysteine levels.The simultaneous deprivation of nitrogen and sulphur in plants leads to an alteration in their metabolism; high levels of glutathione (GSH) in the shoots could signify the induction of a mechanism intended for coping with stressful conditions.Sulphate deprivation enhanced OASTL activity, mainly in the roots; on the other hand, OASTL increases observed under S deprivation were clearly dependent on the nitrogen availability in the culture medium. In fact, the nitrate supply to the N and S starved plants that showed OASTL activity very low, rapidly recovered the OASTL activities to the levels typical of control plants. Nevertheless, the ammonium supply had negligible effects on the OASTL activity only observed after three days in the roots.Our results support the hypothesis that in barley plants, a portion of S assimilation (up to cysteine biosynthesis) occurs in the roots, and a reciprocal influence of nitrogen assimilation on cysteine synthesis occurs.

The effect of silicon on the symptoms of manganese toxicity in maize plants

The effect of exogenously applied silicon (Si) on plant growth, lipid peroxidation, total phenolic compounds and non-protein thiols was studied in two maize varieties (Zea mays L. vars. Kneja 605, 434) differing in sensitivity to excess manganese (Mn). Based on the density of brown spots per leaf area and relative shoot weight (RSW) used to define Mn tolerance var. Kneja 434 was found to be more Mn-tolerant than Kneja 605. The lipid peroxidation level and total phenolic compounds were enhanced with increasing Mn concentration in the nutrient solution. In addition, the Mn-sensitive var. Kneja 605 with markedly expressed first visible Mn toxicity symptoms had higher levels of total phenolic acids than var. Kneja 434 thus supporting the hypothesis that a stimulating effect of Mn on phenol content reflected rather a stress response to Mn excess than a tolerance mechanism. In contrast, non-protein SH content increased to a higher extent in the Mn-tolerant var. Kneja 434. The increased amount of non-protein SH compounds was accompanied by a much stronger oxidative stress in the Mn-sensitive plants when compared with the Mn-tolerant variety, thus suggesting that non-protein SH compounds may play a role in Mn tolerance in maize. The addition of silicon (Si) reduced the density of brown spots per leaf area as well as lipid peroxidation level and improved plant growth in Mn-treated plants.

Occurrence, Synthesis, and Mammalian Cell Cytotoxicity and Genotoxicity of Haloacetamides: An Emerging Class of Nitrogenous Drinking Water Disinfection Byproducts

The haloacetamides, a class of emerging nitrogenous drinking water disinfection byproduct (DBPs), were analyzed for their chronic cytotoxicity and for the induction of genomic DNA damage in Chinese hamster ovary cells. The rank order for cytotoxicity of 13 haloacetamides was DIAcAm > IAcAm > BAcAm > TBAcAm > BIAcAm > DBCAcAm > CIAcAm > BDCAcAm > DBAcAm > BCAcAm > CAcAm > DCAcAm > TCAcAm. The rank order of their genotoxicity was TBAcAm > DIAcAm approximately equal to IAcAm > BAcAm > DBCAcAm > BIAcAm > BDCAcAm > CIAcAm > BCAcAm > DBAcAm > CAcAm > TCAcAm. DCAcAm was not genotoxic. Cytotoxicity and genotoxicity were primarily determined by the leaving tendency of the halogens and followed the order I > Br > > Cl. With the exception of brominated trihaloacetamides, most of the toxicity rank order was consistent with structure-activity relationship expectations. For di- and trihaloacetamides, the presence of at least one good leaving halogen group (I or Br but not Cl) appears to be critical for significant toxic activity. Log P was not a factor for monohaloacetamides but may play a role in the genotoxicity of trihaloacetamides and possible activation of dihaloacetamides by intracellular GSH and -SH compounds.

An ab initio and DFT study of the interaction between ethanethiol and zeolites

The interaction of ethanethiol (C 2H 5SH) with a model cluster of three tetrahedral zeolite sites (T3) and a larger zeolite model represented by a 12-membered ring with one hydroxyl Brönsted acid site (T12), has been investigated by Hartree–Fock (HF) and the B3LYP approach of the density functional theory methods using the 6-31+G(d,p) basis set. The molecular formula of the T12 cluster is Al(OH) 2(OH)(SiOH 2) 11. The deprotonation energy was evaluated for the T3 and T12 clusters as a criterion to account for the acidity strength of the zeolite models. The interaction between C 2H 5SH and these clusters leads to the formation of planar vander Waals 1:1 adsorption complexes, dominated by hydrogen bonding between the S atom of C 2H 5SH and the H atom of the hydroxyl group in the Al–O–Si zeolite bridge. The results of structures and interaction energies, show that these complexes are similar to other sulfur–zeolite complexes reported in the literature. A vibrational analysis was also performed to estimate the shift of frequency of the OH vibrational mode of the zeolite hydroxyl group on coordination, where the corresponding shifts are negative and are of the same order of magnitude as the corresponding experimental values shown by R–SH compounds adsorbed on SiO 2 and acidic zeolites. Additionally, the SH mode frequency shift in ethanethiol complex is positive. The size of the cluster is significant for the estimation of the properties of the ethanethiol–zeolite adsorption complex.

Physiological behaviour, oxidative damage and antioxidative protection of olive trees grown under different irrigation regimes

Irrigation effects were investigated on an 8-year-old olive (Olea europaea L., cv. Cobrancosa) commercial orchard located in northeast Portugal. Trees were subjected to a rainfed control (T0) and three treatments (T1, T2, T3) that received a seasonal water amount equivalent to 30%, 60% and 100% of the estimated local evaporative demand by a drip irrigation system. Irrigation increases the photosynthetic activity of olive trees, in association with increases in water status, and reduces the midday and afternoon depression in gas exchange. The closely association between photosynthetic rate (A) and stomatal conductance (gs) revealed that the decline in net photosynthesis over the course of the day was largely a consequence of stomatal limitation. However, the ratio of intercellular to atmospheric CO2 concentration increased markedly from morning to midday in non-irrigated plants, in spite of lower gs, suggesting that non-stomatal limitations of photosynthesis also occur when environmental conditions become more stressful. The occurrence of perturbations at chloroplastic level in rainfed plants was demonstrated by a lower maximum photochemical efficiency of photosystem II during the afternoon. Chlorophyll fluorescence measurements also revealed the occurrence of a dynamic photoinhibition in irrigated trees, mainly in T2 and T3, which seemed to be effective in protecting the photosynthetic apparatus from photodamage. Irrigation enhances antioxidant protection and decreases the oxidative damage at leaf level. Leaves grown under rainfed conditions revealed symptoms of oxidative stress, like the reduction (14%) in chlorophyll concentration and the increased levels (57%) of lipid peroxidation. We also found that the scavenging function of superoxide dismutase was impaired in rainfed plants. In contrast, the low thiobarbituric acid reactive substances concentration in T3 indicates that irrigation enhances the repairing mechanisms and decreases the oxidative damage by lipid peroxidation. Accordingly, leaves in T3 treatment had high levels of –SH compounds and the highest antioxidant potential. Meanwhile, the finding that guaiacol peroxidase activity increased in rainfed plants, associated with the appearance of oxidative damage, suggests that this enzyme has no major antioxidative function in olive.

Mechanism of DNA damage induced by bromate differs from general types of oxidative stress

A representative reactive oxygen species (ROS), hydroxyl radical ( OH), is a highly reactive species and induces DNA backbone breakage. OH also oxidizes every DNA base. The interaction of OH with guanine leads to the generation of not only piperidine-resistant 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) but also various piperidine-labile products. On the other hand, potassium bromate (KBrO 3) induces specific formation of 8-oxodG in the presence of SH compounds, such as glutathione (GSH) and cysteine (Cys). GSH/Cys reduces KBrO 3 (BrO 3 −) to BrO 2, which abstracts one electron from guanine. The one-electron oxidation of guanine may yield cation radicals followed by the reaction with a water molecule, leading to 8-oxodG formation. Therefore, mechanism of bromate-induced oxidative DNA damage is different from general types of oxidative stress such as OH.

Oxidative DNA damage in cultured fibroblasts from patients with hereditary glutathione synthetase deficiency

The SH compound glutathione (GSH) is involved in several fundamental functions in the cell, including protection against reactive oxygen species (ROS). Here, we studied the effect on oxidative DNA damage in cultured skin fibroblasts from patients with hereditary GSH synthetase deficiency. Our hypothesis was that GSH-deficient cells are more prone to DNA damage than control cells. Single cell gel electrophoresis (the comet assay) in combination with the formamidopyrimidine DNA glycosylase enzyme, which recognizes oxidative base modifications, was used on cultured fibroblasts from 11 patients with GSH synthetase deficiency and five control subjects. Contrary to this hypothesis, we found no significant difference in background levels of DNA damage between cells from patients and control subjects. To study the induction of oxidative DNA damage without simultaneous DNA repair, the cells were γ-irradiated on ice and DNA single-strand breaks measured. The patient and control cells were equally sensitive to induction of single strand breaks by γ-irradiation. Therefore, factors other than GSH protect DNA from oxidative damage. However, cells with a high background level of oxidative DNA damage were found to be more sensitive to ionizing radiation. This suggests that differences in background levels of oxidative DNA damage may depend on the cells' intrinsic protection against induction of oxidative damage.

Reactivity studies with gold-supported molybdenum nanoparticles

The reconstructed (22 × √3)-Au(1 1 1) surface was used as a template and inert support for depositing Mo nanoparticles for reactivity studies of desulfurization and the formation of MoS x nanoparticles. Nanoparticles of Mo were prepared on the Au(1 1 1) substrate by two methods: physical vapor deposition (PVD) of Mo and UV-assisted chemical vapor deposition (UV-CVD) through a molybdenum hexacarbonyl precursor. STM studies have shown that the Mo nanoparticles are thermodynamically unstable on the Au(1 1 1) surface, and that gold encapsulates Mo at temperatures above 300 K. Reactivity studies using Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) show that bare Mo nanoparticles are very reactive and can cause complete dissociation of hydrogen sulfide, methyl mercaptan, and thiophene. The presence of gold atoms on the Mo nanoparticles modifies their reactivity. In the case of H 2S and CH 3SH, the overall activity for desufurization is unaffected by gold encapsulation; however, the selectivity to form methane from CH 3SH increased from 20% on bare Mo particles to 60% on gold-covered Mo particles. In contrast, gold-encapsulated Mo nanoparticles are relatively inert towards dissociation of thiophene. We believe that the interaction of R–SH compounds with Au-encapsulated Mo nanoparticles proceeds through intermediacy of surface gold thiolates.

Cadmium accumulation in Allium schoenoprasum L. grown in an aqueous medium

The ability of Allium s choenoprasum L. (chives) to accumulate and tolerate cadmium in aqueous Hoagland medium at 50 μM and 250 μM was tested under continuous growth or several successive harvests of shoots. After 28 days of continuous growth, chives accumulated the metal up to 0.2% and 0.5% of its dry weight, when grown in 50 μM and 250 μM, respectively. In experiments that the leaves were successively harvested every 16 days, there were no obvious stress symptoms after six harvests during a period of 96 days at 50 μM Cd. At 250 μM, after 64 days and four harvests, inhibition of growth occurred. In each treatment, a total of 1.2 g kg −1 DW and 2.4 g kg −1 DW was accumulated in the leaves, respectively. Total SH compounds concentration in leaf was found significantly higher by 3 and 7.4 times in plants treated with Cd at 50 μM and 250 μM in comparison to the control, respectively, while no difference in the concentration of glutathione (GSH + GSSG) was found. Thus, it is assumed that sulphur-containing compounds, yet unknown, are involved in defensive mechanisms against heavy metals in chives. The results presented, point to chives phytoremediation potential, but also on the potential risk in accumulation of heavy metals in a commonly edible plant.

Role of sulphur availability on cadmium-induced changes of nitrogen and sulphur metabolism in maize ( Zea mays L.) leaves

The interactions between sulphur nutrition and Cd exposure were investigated in maize ( Zea mays L.) plants. Plants were grown for 12 days in nutrient solution with or without sulphate. Half of the plants of each treatment were then supplied with 100 μM Cd. Leaves were collected 0, 1, 2, 3, 4 and 5 days from the beginning of Cd application and used for chemical analysis and enzyme assays. Cd exposure produced symptoms of toxicity (leaf chlorosis, growth reduction) and induced a noticeable accumulation of non-protein SH compounds. As phytochelatins are glutamate- and cysteine-rich peptides, the effect of cadmium on some enzyme activities involved in N and S metabolism of maize leaves was studied in relation to the plant sulphur supply. In vivo Cd application to S-sufficient plants resulted in a drop of all measured enzyme activities. On the other hand, S-deficient plants showed a decrease in nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2) activity, and an increase in NAD-dependent glutamate dehydrogenase (GDH; EC 1.4.1.2) and phosphoenolpyruvate carboxylase (PEPc; EC 4.1.1.31) activity as a result of the Cd treatment. Furthermore, in the same plants ATP sulphurylase (ATPs; EC 2.7.7.4) and O-acetylserine sulphydrylase (OASs; EC 4.2.99.8) showed a particular pattern as both enzymes exhibited a transient maximum value of activity after 4 days from the beginning of Cd exposure. Results provide evidence that the increase of ATPs, OASs, GDH and PEPc activities, observed exclusively in S-deficient Cd-treated plants, may be part of the defence mechanism based on the production of phytochelatins.

Does the Sulfur Assimilation Pathway Play a Role in the Response to Fe Deficiency in Maize (Zea mays L.) Plants?

The finding that the methionine is the sole precursor of the mugineic acid family phytosiderophores induced us to evaluate whether sulfur assimilation pathway has a role in plant response to Fe deficiency. Maize plants were grown for 10 days in nutrient solution (NS) containing 80 µM Fe in the presence (+S) or absence (−S) of sulfate. After removing the root extraplasmatic iron pool, half of the plants of each treatment (+S and −S) were transferred to a new Fe deficient NS (0.1 µM final Fe concentration) (−Fe). The remaining plants of each pre‐culture condition (+S and −S) were transferred to a new NS containing 80 µM Fe (+Fe). Leaves were collected 4 and 24 hours from the beginning of Fe deprivation period and used for chemical analysis and enzyme assays. Results showed that iron content in the leaves was lower in plants grown in S‐deficiency than in those grown in the presence of the macro‐nutrient. Iron deprivation produced an increase in the level of SH compounds in both nutritive conditions (+S and −S). These observations are suggestive of some relationship between S nutrition and Fe uptake. For this reason, we next investigated the influence of Fe availability on S metabolism through the evaluation of changes in ATPs and OASs activity, the first and the last enzyme of S assimilation pathway respectively. Results showed that S‐starvation increased the activity of both enzymes, but this effect disappeared in plants upon Fe deficiency suggesting that S metabolism is sensitive to Fe availability. Taken together these evidences suggest that S metabolism is sensitive to soil Fe‐availability for plant nutrition and support the hypothesis of S involvement in plant response to Fe deprivation.

Outcome of patients with rheumatoid arthritis treated by step-wise administration of disease-modifying antirheumatic drugs over a 10-year period

Disease-modifying antirheumatic drugs (DMARDs) are expected to relieve polyarthritis, and thereby improve the patient's quality of life and eventually alter the prognosis of rheumatoid arthritis (RA) or the progressive joint destruction caused by it. DMARDs may cause adverse reactions and become less effective over time in some patients. Using changes in disease activity and X-ray findings as indicators, we retrospectively evaluated the long-term results of the step-wise administration of DMARDs in 200 patients with RA. The patients had been treated with gold compounds, SH compounds, and methotrexate, in this order, over a total of 10 years since initially being diagnosed with the disease in its relatively early stages. The step-wise administration of DMARDs had decreased and controlled RA activity and inflammatory response over the 10 years. Although X-ray findings for the wrists worsened over time in most of the patients, no knee or hip joint destruction was observed in patients in whom disease activity had been controlled well for a long period of time. The progression of destruction of major joints can be prevented in cases in which the Lansbury activity index and C-reactive protein are maintained at levels not more than 30% and 1.5 mg/dl, respectively. Since no drugs are now available which specifically prevent the progression of joint destruction, it is important to control RA activity for as long as possible.

変異原の生成・低減と抗酸化剤

Food antioxidants or reductones, ascorbic acid and its derivatives, monophenolics including α-tocopherol, polyphenolics in tea leaves and red wine, SH compounds including cysteine, carotenoids including β-carotene and other reductones, can scavenge reactive oxygen species, reactive nitrogen oxide species and lipid peroxy radicals. By contrast, these antioxidants or reductones can be converted into prooxidants in the presence of oxygen or act to produce harmful compounds. Formation of heterocyclic amine mutagens in the model system is inhibited by scavenging pyrazine cation radical with monophenolics, polyphenolics, ascorbate and SH compounds, and the mutagenicity in cooked hamburger is effectively inhibited by ascorbate. Formation of nitrosamines is effectively inhibited by ascorbate, but inhibited or stimulated by polyphenolics and monophenolics. Monophenolics are converted into possibly harmful nitroso-, nitro- and diazo-compounds by reaction with N2O3. Hydroxyfuranones found in the Maillard reactions and hydroxyhydroquinone found in coffee cause DNA single strand breaks by generation of reactive oxygen species, and cause lung lipid peroxidation and increased type IV and I allergy responses by oral administration to experimental animals. On the other hand, food polyunsaturated fatty acids, which has been so far considered to give deteriorate effect, are found to be protective against oxidative stress-induced DNA damage.

Glutathione-dependent system of antioxidant defense in the placenta in preterm delivery.

Components of the antioxidant defense system in placental tissues were studied in women with normal pregnancy and full-term delivery and women with spontaneous abortions at 28-36 weeks. In women with spontaneous abortions glutathione peroxidase activity in placental tissues increased and the content of SH compounds decreased, which led to exhaustion of the antioxidant defense system. Glutathione-S-transferase activity also decreased, which attests to impaired detoxifying function of the placenta.

Tn5044-conferred mercury resistance depends on temperature: the complexity of the character of thermosensitivity.

Escherichia coli K12 containing the transposon Tn5044 mer operon (merR, T, P, C, and A genes) is resistant to mercuric chloride at 30 degrees C but sensitive to this compound at 37-41.5 degrees C. We have studied the mechanism underlying the temperature-sensitive nature of this mercury resistance phenotype, and found that the expression of the Tn5044 merA gene coding for mercuric reductase (MerA) is severely inhibited at non-permissive temperatures. Additionally, MerA showed a considerably reduced functional activity in vivo at non-permissive temperatures. However, the temperature-sensitive character of the functioning of this enzyme in cell extracts, where it interacted with one of the low-molecular weight SH compounds rather than with the transport protein MerT (as is the case in vivo), was not apparent. These data suggest that the temperature-sensitive mercury resistance phenotype should stay under control at two stages: when the merA gene is expressed and when its product interacts with MerT to accept the mercuric ion.

Cystine analyses of separate day and night urine as a basis for the management of patients with homozygous cystinuria.

Based on previous observations of the diurnal variation of urinary cystine excretion, the use of separate day and night urine collections was proposed. To improve the medical treatment of patients with cystinuria, this strategy was performed to guide the fluid intake and the administration of SH compounds (tiopronin, D-penicillamine, and MESNA).Twenty-six patients (19 treated with SH compounds and seven with alkalinization and hydration only) were followed during two 3.5-year periods. During Period 1, 24-h urine was collected and during Period 2, separate day and night urine was collected. There were 56 episodes of high urinary cystine supersaturation (> 1,200 micromol/l) during Period 2, 47% of which would have evaded detection with 24-h urine analysis. In comparison with Period 1, the urinary cystine concentration was lower (P < 0.05), and the urinary volume was higher (P < 0.05) during Period 2. Patients treated with tiopronin had reduced cystine excretion (P < 0.05) and at the end of Period 2, an increased dose of tiopronin, reflecting a more aggressive treatment. Furthermore, a reduced number of stone episodes and need of active stone removal (P < 0.05) was noted in the whole group of patients. Analyses of separate day and night urine samples can be used advantageously to reveal episodes of high supersaturation with cystine not detected in 24-h urine samples. Such a procedure might be useful for optimizing the treatment of patients with cystinuria.

Requirement of glutathione and cysteine in guanine-specific oxidation of DNA by carcinogenic potassium bromate.

Potassium bromate (KBrO3), a food additive, induces renal-cell tumors in rats. KBrO3 induced 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG) formation in human leukemia cell line HL-60 as well as in its H2O2-resistant clone, HP100, suggesting no involvement of H2O2. Depletion of GSH by buthionine sulfoximine (BSO) had a little inhibitory effect on KBrO3-induced 8-oxodG formation. However, the amount of 8-oxodG was still significantly higher than that in control, suggesting that intracellular Cys can affect KBrO3 to oxidize DNA, when GSH decreased. KBrO3 caused 8-oxodG in isolated DNA in the presence of GSH (tripeptide; gamma-GluCysGly), gamma-GluCys, CysGly, or Cys. Methional completely inhibited 8-oxodG formation induced by KBrO3 plus GSH, but typical hydroxyl radical scavengers, SOD and catalase, had little or no inhibitory effects. When bromine solution (BrO(-)) was used instead of BrO3(-), similar scavenger effects were observed. Experiments with 32P-labeled DNA fragments obtained from the human p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene suggested that KBrO3 induced 8-oxodG formation at 5'-site guanine of GG and GGG sequences of double-stranded DNA in the presence of GSH and that treatment of formamidopyrimidine-DNA glycosylase led to chain cleavages at the guanine residues. ESR spin-trapping studies showed that 1:2:2:1 quartet DMPO (5,5-dimethyl-1-pyrroline N-oxide) spectrum similar to DMPO/hydroxy radical (*OH) adduct, but the signals were not inhibited by ethanol. Therefore, the signal seemed not to be due to *OH but byproduct due to oxidation of DMPO by the reactive species. The signals were suppressed by the addition of dGMP, but not by other mononucleotides, suggesting the specific reactivity with guanine. On the basis of our results and previous literature, it is speculated that reduction of KBrO3 by SH compounds in renal proximal tubular cells yields bromine oxides and bromine radicals, which are the reactive species that cause guanine oxidation, leading to renal carcinogenesis of KBrO3.

Covalent glutathione conjugation to cyanobacterial hepatotoxin microcystin LR by F344 rat cytosolic and microsomal glutathione S-transferases

Most investigators report that microcystins (MCs) bound covalently to SH compounds, such as l-cysteine and reduced glutathione (GSH). However, their studies were based on a high pH condition. In the present study, we investigated the reaction between microcystin LR (MCLR) and GSH in various pH conditions. As a result, we found that no MCLR conjugated with GSH in these conditions, and MCLR mixed with GSH showed different peaks of retention time compared with intact MCLR on the high performance liquid chromatography–mass spectrometry (LC–MS) chromatograms. Furthermore, we found the GSH conjugate of MCLR was detected in the glutathione S-transferase (GST) assay using F344 rat liver cytosol and microsomes. This indicates that the covalent GSH conjugation was caused only by an enzymatic activity. We conclude, therefore, that the reaction is caused by enzymatic action and is not due to the Michael reaction.