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PubMed1982

Water disinfection with the hydrogen peroxide-ascorbic acid-copper (II) system.

Treatment of secondary effluents with hydrogen peroxide (10 mg/liter)-ascorbic acid (10 mg/liter)-Cu2+ (0.5 mg/liter) for 60 min resulted in around 99% reduction of the initial plate count. Hydrogen peroxide could be replaced by other peroxygen compounds; ascorbic acid could be replaced by other reducing agents, of which sodium sulfite and ethanol were the most effective. Cu2+, however, could not be replaced by other metal ions without loss of bactericidal efficiency of the ternary combination. Enterobacteriaceae, total and fecal coliforms, staphylococci, and micrococci were reduced by 99.0 to 99.9%. Group D streptococci aerobic spores were reduced by 80 and 15%, respectively. Clostridium perfringens, yeasts, and molds were not killed by the disinfectant combinations. The effect of pH was only minor in the range from 6 to 7.5. At a higher pH value the bactericidal effects tended to decrease. The hydrogen peroxide-ascorbic acid-Cu2+ combination made it possible to obtain 99% reduction within 30 min. When using the hydrogen peroxide-sodium sulfite-Cu2+ or the hydrogen peroxide-ethanol-Cu2+ combinations, 60 min of contact time was necessary to obtain 99% reduction of the initial plate count. Cu2+ combined to an intermediate product of the ascorbic acid autoxidation is the toxic agent, and its penetration into the cell is promoted by hydrogen peroxide.

Ascorbic Acid↗
PubMed1978

Role of hydrogen peroxide and peroxidase in the cytotoxicity of Trypanosoma dionisii by human granulocytes.

The mechanism of the cytotoxic reaction of leukocytes to Trypanosoma dionisii was investigated. Cytotoxicity was measured by release of [99mTc]pertechnetate from labeled protozoa. Both granulocytes and lymphocytes were found to be cytotoxic to antibody-coated T. dionisii. The reaction was inhibited by diethyldithiocarbamate and by potassium cyanide, both of which inhibit myeloperoxidase. Myeloperoxidase from azurophil granules was toxic to T. dionisii, provided that hydrogen peroxide was also present. Hydrogen peroxide formation was induced in granulocytes and, to a lesser extent, in lymphocytes by antibody-coated T. dionisii. Inhibition of this hydrogen peroxide formation by treatment of the effector cell surface with p-diazobenzenesulfonic acid inhibited cytotoxicity. It is therefore concluded that granulocytes, and probably also lymphocytes, kill T. dionisii with hydrogen peroxide by a peroxidase-mediated reaction. Although hydrogen peroxide and myeloperoxidase alone were also cytotoxic to the lymphoblastoid cell line CLA4, it seems unlikely that this is the cytotoxic mechanism for this process because these cells were unable to induce hydrogen peroxide formation.

Animals↗
PubMed2000

A hydrogen peroxide-forming NADH oxidase that functions as an alkyl hydroperoxide reductase in Amphibacillus xylanus.

The Amphibacillus xylanus NADH oxidase, which catalyzes the reduction of oxygen to hydrogen peroxide with beta-NADH, can also reduce hydrogen peroxide to water in the presence of free flavin adenine dinucleotide (FAD) or the small disulfide-containing Salmonella enterica AhpC protein. The enzyme has two disulfide bonds, Cys128-Cys131 and Cys337-Cys340, which can act as redox centers in addition to the enzyme-bound FAD (K. Ohnishi, Y. Niimura, M. Hidaka, H. Masaki, H. Suzuki, T. Uozumi, and T. Nishino, J. Biol. Chem. 270:5812-5817, 1995). The NADH-FAD reductase activity was directly dependent on the FAD concentration, with a second-order rate constant of approximately 2.0 x 10(6) M(-1) s(-1). Rapid-reaction studies showed that the reduction of free flavin occurred through enzyme-bound FAD, which was reduced by NADH. The peroxidase activity of NADH oxidase in the presence of FAD resulted from reduction of peroxide by free FADH(2) reduced via enzyme-bound FAD. This peroxidase activity was markedly decreased in the presence of oxygen, since the free FADH(2) is easily oxidized by oxygen, indicating that this enzyme system is unlikely to be functional in aerobic growing cells. The A. xylanus ahpC gene was cloned and overexpressed in Escherichia coli. When the NADH oxidase was coupled with A. xylanus AhpC, the peroxidase activity was not inhibited by oxygen. The V(max) values for hydrogen peroxide and cumene hydroperoxide reduction were both approximately 150 s(-1). The K(m) values for hydrogen peroxide and cumene hydroperoxide were too low to allow accurate determination of their values. Both AhpC and NADH oxidase were induced under aerobic conditions, a clear indication that these proteins are involved in the removal of peroxides under aerobic growing conditions.

Amino Acid Sequence↗
PubMed2000

The redox-sensitive transcriptional activator OxyR regulates the peroxide response regulon in the obligate anaerobe Bacteroides fragilis.

The peroxide response-inducible genes ahpCF, dps, and katB in the obligate anaerobe Bacteroides fragilis are controlled by the redox-sensitive transcriptional activator OxyR. This is the first functional oxidative stress regulator identified and characterized in anaerobic bacteria. oxyR and dps were found to be divergently transcribed, with an overlap in their respective promoter regulatory regions. B. fragilis OxyR and Dps proteins showed high identity to homologues from a closely related anaerobe, Porphyromonas gingivalis. Northern blot analysis revealed that oxyR was expressed as a monocistronic 1-kb mRNA and that dps mRNA was approximately 500 bases in length. dps mRNA was induced over 500-fold by oxidative stress in the parent strain and was constitutively induced in the peroxide-resistant mutant IB263. The constitutive peroxide response in strain IB263 was shown to have resulted from a missense mutation at codon 202 (GAT to GGT) of the oxyR gene [oxyR(Con)] with a predicted D202G substitution in the OxyR protein. Transcriptional fusion analysis revealed that deletion of oxyR abolished the induction of ahpC and katB following treatment with hydrogen peroxide or oxygen exposure. However, dps expression was induced approximately fourfold by oxygen exposure in DeltaoxyR strains but not by hydrogen peroxide. This indicates that dps expression is also under the control of an oxygen-dependent OxyR-independent mechanism. Complementation of DeltaoxyR mutant strains with wild-type oxyR and oxyR(Con) restored the inducible peroxide response and the constitutive response of the ahpCF, katB, and dps genes, respectively. However, overexpression of OxyR abolished the catalase activity but not katB expression, suggesting that higher levels of intracellular OxyR may be involved in other physiological processes. Analysis of oxyR expression in the parents and in DeltaoxyR and overexpressing oxyR strains by Northern blotting and oxyR'::xylB fusions revealed that B. fragilis OxyR does not control its own expression.

Amino Acid Sequence↗
PubMed2001

DNA microarray-mediated transcriptional profiling of the Escherichia coli response to hydrogen peroxide.

The genome-wide transcription profile of Escherichia coli cells treated with hydrogen peroxide was examined with a DNA microarray composed of 4,169 E. coli open reading frames. By measuring gene expression in isogenic wild-type and oxyR deletion strains, we confirmed that the peroxide response regulator OxyR activates most of the highly hydrogen peroxide-inducible genes. The DNA microarray measurements allowed the identification of several new OxyR-activated genes, including the hemH heme biosynthetic gene; the six-gene suf operon, which may participate in Fe-S cluster assembly or repair; and four genes of unknown function. We also identified several genes, including uxuA, encoding mannonate hydrolase, whose expression might be repressed by OxyR, since their expression was elevated in the DeltaoxyR mutant strain. In addition, the induction of some genes was found to be OxyR independent, indicating the existence of other peroxide sensors and regulators in E. coli. For example, the isc operon, which specifies Fe-S cluster formation and repair activities, was induced by hydrogen peroxide in strains lacking either OxyR or the superoxide response regulators SoxRS. These results expand our understanding of the oxidative stress response and raise interesting questions regarding the nature of other regulators that modulate gene expression in response to hydrogen peroxide.

Bacterial Proteins↗
PubMed1994

Resistance of erythrocytes to lipid peroxidation in alcoholic patients.

The ability of erythrocytes to resist lipid peroxidation may be a useful marker of antioxidant status in alcoholic patients, in whom depletion of dietary antioxidants may combine with increased production of free radicals to produce liver damage. There are conflicting reports, however, on the resistance of erythrocytes from alcoholic patients to lipid peroxidation. This study examined the relation between the degree of alcohol induced liver disease and the resistance of erythrocytes to chemically induced lipid peroxidation, measuring lipid peroxidation as malondialdehyde production. Erythrocytes from alcoholic patients with Child's C cirrhosis had significantly increased resistance to lipid peroxidation compared with both controls (p < 0.001) and alcoholic patients with moderate liver disease (p < 0.001). There was no difference between alcoholic patients with moderate liver disease and controls. Increased resistance to free radical initiated lipid peroxidation in alcoholic patients is related to liver damage rather than to alcohol abuse alone. This could arise from changes in the lipid composition of the erythrocyte membranes resulting from abnormal liver function. Tests of antioxidant status based upon the resistance of erythrocytes to free radical stress in vitro may therefore be flawed when such changes in membrane lipid composition can occur.

Adult↗
PubMed2002

Associated changes of lipid peroxidation and transforming growth factor beta1 levels in human colon cancer during tumour progression.

BACKGROUND: During neoplastic progression, alterations in transforming growth factor beta1 (TGF-beta1) dependent control of cell growth may be an important mechanism of selective proliferation of transformed cellular clones. Defective regulation of TGF-beta1 receptors has been reported to occur in a number of human malignant tumours while little is known of the actual levels of this growth inhibitory cytokine in cancer. On the basis of the demonstrated ability of major lipid peroxidation products such as 4-hydroxynonenal to modulate TGF-beta1 expression and synthesis, we speculated that decreased lipid oxidation, as frequently observed in neoplastic tissues, would contribute to the selective promotion of tumour growth through decreased expression of the cytokine within the tumour mass. AIMS: To seek a possible association between steady state levels of major aldehydic end products of lipid peroxidation and TGF-beta1 content in human colon cancer at different stages of growth. PATIENTS AND METHODS: Tissue biopsies from 15 adult patients with colon adenocarcinoma of different TNM and G stagings were compared with regard to lipid peroxidation aldehydes and net TGF-beta1 levels. For a more comprehensive analysis, cytokine type I and II receptors were measured in tumour biopsies. In one set of experiments, to support the conclusions, the apoptotic effect of TGF-beta1 was evaluated in a human colon cancer cell line, CaCo-2, retaining receptor changes consistent with those observed in cancer patients. RESULTS: With the exception of two extremely advanced cases (T4/G3) in which tissue levels of lipid peroxidation were within the normal range, 4-hydroxynonenal was significantly decreased in all other cancer specimens. Consistent with lipid peroxidation levels, TGF-beta1 protein was markedly decreased or even negligible compared with the corresponding normal tissue surrounding the tumour in all tested biopsies except for the two T4/G3 colon cancers in which cytokine content was again within the normal range. As regards TGF-beta1 receptors, both in tumour sections and CaCo-2 cells, downregulation was greater for TGF-beta1 receptor I than for receptor II. Of note, in CaCo-2 cells, incubation with appropriate doses of TGF-beta1 led to marked nuclear fragmentation and apoptosis. CONCLUSIONS: Evasion of human colon cancer cells from TGF-beta1 mediated growth inhibition appears to be due not only to downregulation of TGF-beta1 receptors, which is inconsistent and unrelated to cancer development, but also to the constant low concentration of this cytokine in the tumour mass. The associated levels of lipid peroxidation aldehydes, much lower than in control tissue, probably represent a lower stimulus for TGF-beta1 production in the neoplastic area and thus a favourable condition for neoplastic progression.

Adenocarcinoma↗
PubMed1999

The role of catalase in hydrogen peroxide resistance in fission yeast Schizosaccharomyces pombe.

The role of catalase in hydrogen peroxide resistance in Schizosaccharomyces pombe was investigated. A catalase gene disruptant completely lacking catalase activity is more sensitive to hydrogen peroxide than the parent strain. The mutant does not acquire hydrogen peroxide resistance by osmotic stress, a treatment that induces catalase activity in the wild-type cells. The growth rate of the disruptant is not different from that of the parent strain. Additionally, transformed cells that overexpress the catalase activity are more resistant to hydrogen peroxide than wildtype cells with normal catalase activity. These results indicate that the catalase of S. pombe plays an important role in resistance to high concentrations of hydrogen peroxide but offers little in the way of protection from the hydrogen peroxide generated in small amounts under normal growth conditions.

Acatalasia↗
PubMed1988

Contracture and cell damage in calcium paradox is not caused by lipid peroxidation.

The role of oxygen radicals and lipid peroxidation in calcium-paradox injury in isolated perfused rat hearts was studied by examining the effects of mannitol and (or) allopurinol on this phenomenon. Myocardial changes due to calcium paradox were characterized by contractile failure, a rise in resting tension, and cell damage. These changes were also accompanied by increased lipid peroxidation, as indicated by an increase in malondialdehyde content. Mannitol (an effective quencher of hydroxyl radicals) treatment resulted in a dose-dependent decrease in lipid peroxidation but did not affect other changes due to calcium paradox. Allopurinol (an inhibitor of xanthine oxidase) neither affected lipid peroxidation nor modified any of the structure-function changes due to calcium paradox. These data demonstrate the occurrence of lipid peroxidation which, however, may not be involved in the observed structure-function changes due to calcium paradox. It is also suggested that in this experimental model, xanthine oxidase may not be the inducer of oxygen radicals or of lipid peroxidation.

Allopurinol↗
PubMed2003

The inhibitory effects of 12 medicinal plants and their component compounds on lipid peroxidation.

The antioxidative activities of 12 medicinal plants and the compounds isolated from them were investigated using the thiocyanate method to evaluate inhibitory effects on lipid peroxidation in the linoleic acid system. The peroxide levels gradually increased during incubation in the presence of linoleic acid over 3 days, and most of the plants inhibited lipid peroxidation. In particular, of the plants tested, Cudrania tricuspidata, Zanthoxylum piperitum, Houttuynia cordata and Ulmus parvifolia reduced lipid peroxidation more effectively as lipid peroxidation progressed, resulting in inhibition of about 80% relative to the control value by the 3rd day of incubation. In addition, the polyphenols isolated from the plants also showed marked and dose-dependent inhibitory effects on lipid peroxidation. The compounds with the strongest activities were 3,4-dihydroxylbenzoic acid, quercetin, the quercetin glycosides quercetin-3-O-beta-D-galactoside, quercetin-3-O-alpha-L-rhamnoside, quercetin-3-O-beta-D-glucoside and quercetin-3-O-rutinose, catechin, gallic acid, methyl gallate and rosamultin isolated from Zanthoxylum piperitum, Houttuynia cordata, Rosa rugosa and Cedrela sinensis. Moreover, quercetin glycosides showed stronger activity than quercetin, suggesting that glycosylation increases the antioxidative activity of quercetin. Our results indicate that the medicinal plants and their polyphenols show promise as therapeutic agents for various disorders involving free radical reactions.

Drugs, Chinese Herbal↗
PubMed1997

Neutrophil-mediated phospholipid peroxidation assessed by gas chromatography-mass spectroscopy.

Disease pathophysiology frequently involves manifestations of the systemic inflammatory response syndrome. Oxyradicals represent key inflammatory mediators, and neutrophils are one important source of oxyradicals. This investigation examined neutrophil-mediated peroxidation of dilinoleoyl phosphatidyl-choline (DLPC) liposomes by monitoring the appearance of monohydroxyl linoleic acid with the use of gas chromatography-mass spectroscopy (GC-MS), compared with traditional assessment of thiobarbituric acid-reactive species (TBARS) and phosphatidylcholine-specific conjugated dienes. DLPC was peroxidized in a system using activated neutrophils in balanced salt solution containing chelated iron. 9-Monohydroxyl linoleic acid and 13-monohydroxyl linoleic acid were readily identified in neutrophil-mediated peroxidized DLPC with the use of GC-MS. Neutrophil NADPH oxidoreductase specific activity correlated highly with total ion current or specific ion monitoring of integrated peak areas for peroxidized linoleic acid but correlated poorly with DLPC-derived TBARS or conjugated dienes. These results ascertain that activated neutrophils mediate phosphatidylcholine lipid peroxidation to specific products, which may be precisely monitored with the use of GC-MS. The extent of this peroxidation is highly correlated with the magnitude of the neutrophil respiratory burst.

Gas Chromatography-Mass Spectrometry↗
PubMed1996

Vitamin E decreases hepatic levels of aldehyde-derived peroxidation products in rats with iron overload.

Hepatic iron overload can cause lipid peroxidation with the formation of aldehydic products, hepatocellular injury, and fibrosis. Vitamin E (alpha-tocopherol) may prevent peroxidation-induced hepatic damage. We used confocal laser scanning microscopy, digital image analysis, and immunohistochemical methods to quantitate aldehyde-derived peroxidation products in the liver of rats with experimental iron overload with or without supplemental vitamin E. A strong autofluorescent reaction colocalizing with iron deposits was present in the livers of iron-loaded rats. Fluorescent granules were unevenly distributed in the cytosol of both hepatocytes and Kupffer cells in the periportal regions. Immunohistochemical studies revealed the presence of malon-dialdehyde adducts in the periportal regions of the ironloaded rats. Vitamin E supplementation markedly reduced the fluorescence intensity and the amount of aldehyde-derived peroxidation products and changed the distribution of stainable iron and iron-associated peroxidation products such that their levels were much decreased in Kupffer cells. These results indicate that aldehyde-derived covalent chemical addition products are formed in the liver in iron overload. Vitamin E supplementation markedly reduces the amount of these compounds and changes their cellular distribution. These findings should be implicated in the role of antioxidant therapy in conditions causing iron overload and lipid peroxidation.

Aldehydes↗
PubMed1992

Peroxide inactivates calcium pumps in pig coronary artery.

To study the effects of hydrogen peroxide, pig coronary artery smooth muscle subcellular fractions enriched in plasma membrane (F2) or sarcoplasmic reticulum (F3) were incubated in various concentrations of peroxide and 5 mM azide. ATP-dependent azide-insensitive oxalate-stimulated Ca2+ uptake was determined for F3 and phosphate-stimulated uptake for F2. Only 1.5-5 microM hydrogen peroxide was required for 50% inhibition of the Ca2+ uptake by F3, but the corresponding concentration for F2 was 10-50 microM. This effect was not prevented by superoxide dismutase. Hydrogen peroxide inhibited the Ca(2+)-dependent formation of a 115-kDa acylphosphate band in F3 and 140- and 115-kDa bands in F2. The inhibition of Ca2+ uptake in F3, however, exceeded the inhibition of the acylphosphate formation. Efflux of Ca2+ from F2 and F3 was enhanced by hydrogen peroxide but F3 was more sensitive than F2. We conclude that hydrogen peroxide has dual effect on Ca2+ dynamics in the coronary artery smooth muscle, i.e., it inactivates the Ca2+ pumps and increases membrane permeability to Ca2+. The effect is more pronounced on sarcoplasmic reticulum than on plasma membrane. Intrinsic catalase may, however, provide partial protection against such damage.

Animals↗
PubMed1995

Increased thromboxane-mediated contractions of retinal vessels of newborn pigs to peroxides.

The vasomotor effects of three peroxides (H2O2, cumene hydroperoxide, and t-butyl hydroperoxide) on the retinal vasculature, as well as the role of thromboxane in these effects, were studied using time-frame photography of isolated eyecup preparations from newborn and adult pigs. All three peroxides caused constriction of retinal arteries and veins, and these effects were greater in the newborn than in the adult. The cyclooxygenase inhibitor indomethacin, the thromboxane synthase blocker CGS-13080, and the thromboxane receptor blockers GR-32191B and L-670,596 inhibited the peroxide-induced vasoconstriction. The peroxides also increased thromboxane levels in the retina, and this increase was greater in newborn than in adult tissues. Both indomethacin and CGS-13080 prevented the peroxide-induced increase in retinal thromboxane. The thromboxane analogue U-46619 also produced constriction of newborn and adult retinal vessels, but its effects on the retinal veins of newborn pigs were less than those on adult veins. Data indicate an important role for increased production of thromboxane in the relative increase in the vasoconstrictor effects of peroxides on the newborn retinal vasculature. These findings suggest that the vasoconstriction and occlusion after oxidative stresses, which precede retinal neovascularization, are mediated by thromboxane.

Aging↗
PubMed1995

Rat mesothelial and tracheal epithelial cells show equal DNA sensitivity to hydrogen peroxide-induced oxidant injury.

To study the relative sensitivity of rat tracheal epithelial and mesothelial cell DNA to oxidant damage, we used the comet assay, a gel microelectrophoresis method that allows visual determination of DNA strand breaks on a cell-by-cell basis, to evaluate damage after hydrogen peroxide exposure. By both a qualitative and a quantitative assay, tracheal epithelial mesothelial cells demonstrated a similar dose-response increase in the number of cells showing strand breaks and the number of breaks per cell after exposure to increasing concentrations of hydrogen peroxide; but even at the highest concentration, some cells failed to show damage. By contrast, 100% of cultured V79 lung fibroblasts showed evidence of damage. Catalase and deferoxamine largely prevented the formation of strand breaks, while superoxide dismutase was not protective. To evaluate DNA repair, cells were exposed to 10 microM hydrogen peroxide for 10 min, washed, and maintained in culture medium; by 2 h the proportion of mesothelial and epithelial cells showing comets had returned to control levels for both cell types. Both cell types also showed a similar pattern of increasing damage after continuous exposure to 10 microM hydrogen peroxide for periods up to 2 h. We conclude that, in this system, 1) mesothelial and tracheobronchial epithelial cells show a similar pattern of DNA injury and repair after hydrogen peroxide exposure; 2) hydrogen peroxide damages DNA of both cell types via a mechanism probably related to the iron-catalyzed formation of hydroxyl radical; and 3) both types of cells appear to be heterogeneous in their sensitivity to oxidant damage, with some cells showing extreme resistance to such damage.

Animals↗
PubMed1998

Exogenous NO enhances hydrogen peroxide-mediated neutrophil adherence to cultured endothelial cells.

One important aspect of oxidant injury is the enhancement of neutrophil-endothelial adhesion by oxidants such as hydrogen peroxide. Recent studies suggest that nitric oxide (NO) can limit oxidant-mediated tissue injury, since inhibitors of endogenous NO synthesis often promote neutrophil-endothelial adhesion. However, less is known about the direct role of exogenous NO in modulating proadhesive effects of oxidants. The objective of this study was to examine how an NO donor modifies hydrogen peroxide-mediated adhesion of neutrophils to cultured endothelial cells. Human umbilical vein endothelial cell monolayers were exposed for 30 min to 0-0.1 mM hydrogen peroxide with or without the NO donor spermine-NONOate (SNO; 0-0.5 mM), and the adhesion of 51Cr-labeled polymorphonuclear neutrophils (PMNs) was measured in a static adhesion assay. PMN adherence was not altered by either peroxide (up to 0.1 mM) or SNO (up to 0.5 mM) alone but was significantly increased by over 300% by coadministration of both 0.1 mM peroxide and 0.5 mM SNO. This increase in adhesion with these two agents was correlated with an increase in the presentation of surface P-selectin but not intercellular adhesion molecule-1. Both PMN adhesion and P-selectin presentation were blocked by 0.1 mM desferrioxamine (an iron chelator) and 1 mM methionine (an oxyradical scavenger). WEB-2086, a platelet-activating factor-receptor antagonist (10 microM), also prevented PMN adhesion but not P-selectin expression. An antibody directed against either P-selectin or intercellular adhesion molecule-1 also blocked adhesion. These data indicate that NO may actually exacerbate rather than protect against the inflammatory effects of peroxide in some models of inflammation through the synthesis of platelet-activating factor and the mobilization of P-selectin.

Azepines↗
PubMed1989

In vivo generation of hydrogen peroxide by rat kidney cortex and glomeruli.

The purpose of this study was to demonstrate in vivo generation of hydrogen peroxide by rat renal cortex and glomeruli. Aminotriazole irreversibly inactivates catalase only in the presence of hydrogen peroxide, and previous studies have shown that aminotriazole-mediated inhibition of catalase is a measure of in vivo changes in the hydrogen peroxide generation. Aminotriazole injected intraperitoneally caused a dose-dependent (0.1-1 g/kg) and a time-dependent (15, 30, 60, 90, 120 min) inhibition of the catalase activity in renal cortex. We confirmed that catalase inactivation by aminotriazole was due to formation of a catalase-hydrogen peroxide intermediate (compound I) because catalase inactivation was prevented by ethanol (2 g/kg), a competitive substrate for compound I. The specific activity of catalase in the glomeruli [0.27 +/- 0.026 k/mg protein (where k is the first-order reaction rate constant), n = 5] was significantly lower than the specific activity in the tubules (1.04 +/- 0.15 k/mg protein, n = 5) obtained from the same rats. The residual catalase activity (RCA) in the glomeruli (0.05 +/- 0.01 k/mg protein) was 19% of control values at 90 min after aminotriazole injection (1 g/kg). Taken together these data provide evidence for in vivo generation of hydrogen peroxide by rat renal cortex and glomeruli under normal conditions. Aminotriazole-mediated inhibition of catalase has been used in previous studies as a measure of in vivo changes in the hydrogen peroxide generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amitrole↗
PubMed1993

Captopril scavenges hydrogen peroxide and reduces, but does not eliminate, oxidant-induced cell injury.

We investigated whether captopril, an angiotensin-converting enzyme (ACE) inhibitor with a sulfhydryl group, enalaprilat, an ACE inhibitor without a sulfhydryl group, and cysteine, an amino acid with a sulfhydryl group but no ACE-inhibiting properties, could scavenge hydrogen peroxide and prevent oxidant-induced cell injury. When 0.1-2.5 mM concentrations of captopril, cysteine, or enalaprilat were incubated with xanthine oxidase and hypoxanthine for 0-120 min, the recovery of hydrogen peroxide was significantly (P < 0.001) reduced in the presence of captopril or cysteine, whereas enalaprilat had no effect on the recovery of hydrogen peroxide. Captopril and cysteine could not scavenge hydrogen peroxide when the sulfhydryl group was blocked with N-ethylmaleimide. When human renal tubular epithelial cells and human umbilical vein endothelial cells were exposed to hydrogen peroxide, oxidant-induced depletion of ATP and efflux of [3H]adenine metabolites was mildly reduced in the presence of captopril or cysteine but was not altered by enalaprilat. Cysteine was more effective in preventing oxidant-induced cell injury than captopril. We conclude that because of its sulfhydryl group, captopril at millimolar concentrations can scavenge hydrogen peroxide and can slightly reduce, but does not eliminate, oxidant-induced cell injury.

Captopril↗