ascorbic-acid and cumene-hydroperoxide

Oxidation-reduction potential describes the balance between the oxidants and antioxidants in fluids including semen. Various artificial culture media are used in andrology and IVF laboratories for sperm preparation and to support the development of fertilized oocytes under in vitro conditions. The composition and conditions of these media are vital for optimal functioning of the gametes. Currently, there are no data on the status of redox potential of sperm processing and assisted reproduction media. The purpose of this study was to compare the oxidation-reduction potential values of the different media and to calibrate the oxidation-reduction potential values of the sperm wash medium using oxidative stress inducer cumene hydroperoxide and antioxidant ascorbic acid. Redox potential was measured in 10 different media ranging from sperm wash media, freezing media and assisted reproductive technology one-step medium to sequential media. Oxidation-reduction potential values of the sequential culture medium and one-step culture medium were lower and significantly different (p < 0.05) from the sperm wash media. Calibration of the sperm wash media using the oxidant cumene hydroperoxide and antioxidant ascorbic acid demonstrated that oxidation-reduction potential and the concentration of oxidant or antioxidant are logarithmically dependent. This study highlights the importance of calibrating the oxidation-reduction potential levels of the sperm wash media in order to utilize it as a reference value to identify the physiological range of oxidation-reduction potential that does not have any adverse effect on normal physiological sperm function.

Topics: Ascorbic Acid; Benzene Derivatives; Calibration; Cryopreservation; Culture Media; Female; Humans; Hydrogen-Ion Concentration; Male; Oxidation-Reduction; Pilot Projects; Reference Values; Reproductive Techniques, Assisted; Semen; Semen Preservation; Spermatozoa

Most animals synthesize ascorbate. It is an essential enzymatic cofactor for the synthesis of a variety of biological molecules and also a powerful antioxidant. There is, however, little direct evidence supporting an antioxidant role for endogenously produced ascorbate. Recently, we demonstrated that incubation of rat hepatocytes with 1-bromoheptane or phorone simultaneously depleted glutathione (GSH) and triggered rapid ascorbate synthesis. The present study investigates the hypothesis that endogenous ascorbate synthesis can confer protection against oxidative stress. Rat and guinea pig hepatocytes were depleted of GSH with 1-bromoheptane and subsequently treated with the oxidative stressor cumene hydroperoxide (CHP) in the presence or absence of the ascorbate synthesis inhibitor sorbinil. In rat hepatocytes, ascorbate content increased linearly (from 15.1 to 35.8 nmol/10(6) cells) over a 105-min incubation. Prior depletion of GSH increased CHP-induced cellular reactive oxygen species (ROS) production, lipid peroxidation, and cell death in rat and guinea pig hepatocytes. Inhibiting ascorbate synthesis, however, further elevated ROS production (2-fold), lipid peroxidation (1.5-fold), and cell death (2-fold) in rat hepatocytes only. This is the first time that endogenous ascorbate synthesis has been shown to decrease cellular susceptibility to oxidative stress. Protection by endogenously produced ascorbate may therefore need to be addressed when extrapolating data to humans from experiments using rodents capable of synthesizing ascorbate.

Topics: Animals; Antioxidants; Ascorbic Acid; Benzene Derivatives; Glutathione; Guinea Pigs; Hepatocytes; Imidazolidines; Ketones; Lipid Peroxidation; Oxidative Stress; Rats; Reactive Oxygen Species

Troglitazone (TGZ) was the first glitazone used for the treatment of type II diabetes mellitus. TGZ undergoes an oxidative chroman ring-opening reaction to form a quinone product. Recently, cytochrome P450 (P450) was shown to be able to catalyze the formation of TGZ quinone. TGZ quinone was the major metabolite formed by dexamethasone-induced rat liver microsomes or myeloperoxidase (MPO) incubated with TGZ. The ultimate source for the quinone carbonyl oxygen atom of TGZ quinone was investigated using (18)O water in both enzyme reaction systems followed by liquid chromatography/tandem mass spectometry analysis of the TGZ quinone product. The resultant TGZ quinone formed by either liver microsomes or MPO contained a single atom of (18)O. The (18)O atom was determined to be the quinone carbonyl oxygen by collision-induced dissociation fragmentation of the (18)O-labeled TGZ quinone. The formation of TGZ quinone was inhibited approximately 90% by coincubation with ascorbic acid or cysteine in the MPO reaction system but only 10 to 20% in liver microsomes, which might reflect the difference in the mechanism by which TGZ quinone is formed by P450 and peroxidase. These results suggest that P450 catalyze an atypical reaction to form TGZ quinone, involving the incorporation of an oxygen from water into the quinone carbonyl position.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Ascorbic Acid; Benzene Derivatives; Carbon Radioisotopes; Catalase; Chromans; Chromatography, Liquid; Cysteine; Dexamethasone; Horseradish Peroxidase; Humans; Iodobenzenes; Male; Microsomes, Liver; Molecular Structure; Oxygen; Oxygen Isotopes; Peroxidase; Quinones; Rats; Rats, Inbred F344; Spectrometry, Mass, Electrospray Ionization; Superoxide Dismutase; Thiazolidinediones; Troglitazone; Water

Approximately 7% of the iron associated with hemoglobin was released from the heme protein during 2 degrees C storage in washed cod muscle. EDTA (2.2 mM) neither accelerated nor inhibited hemoglobin-mediated lipid oxidation based on the formation of lipid peroxides and TBARS. This suggested that low molecular weight iron was a minor contributor to hemoglobin-mediated lipid oxidation in washed cod muscle. Ascorbate (2.2 mM) was a modest to highly effective inhibitor of hemoglobin-mediated lipid oxidation depending on which washed cod preparation was assessed. Experimental evidence suggested that the ability of residual ascorbate to breakdown accumulating lipid hydroperoxides to reactive lipid radicals can explain the shift of ascorbate from an antioxidant to a pro-oxidant. Increasing the lipid peroxide content in washed cod muscle accelerated hemoglobin-mediated lipid oxidation and decreased the ability of ascorbate to inhibit lipid oxidation. Preformed lipid peroxide content in cod muscle was highly variable from fish to fish.

Topics: Animals; Ascorbic Acid; Benzene Derivatives; Fishes; Hemoglobins; Iron; Lipid Peroxidation; Lipid Peroxides; Lipids; Muscles; Thiobarbituric Acid Reactive Substances; Trout

The antioxidant properties of sesame lignans (sesamol, sesamin and sesamolin) were evaluated in comparison to tocols (alpha- and gamma-tocopherols and alpha-tocotrienol) and butylated hydroxytoluene (BHT) using the following in vitro lipid peroxidation systems: (i) rat liver microsomes and cumene hydroperoxide (CumOOH)/Fe2+-ADP-NADPH (enzymatic) or (ii) rat liver mitochondria and Fe2+-ascorbate (nonenzymatic) systems. Sesamol containing a free phenolic group inhibited lipid peroxidation in both the systems whereas sesamin and sesamolin having methylenedioxy groups were effective only in the microsomal system. Since detoxifying enzymes are localized in microsomes, the inhibitory effects of sesamin and sesamolin observed in the microsomal system may be attributed to their metabolites. However, the inhibitory effects of lignans were lower than tocols and BHT. Combination of individual lignans and tocopherols (alpha, gamma) or alpha-tocotrienol showed higher inhibitory effects than the sum of individual inhibitions in CumOOH and Fe2+-ascorbate systems suggesting synergistic interactions. The time course of CumOOH-mediated lipid peroxidation showed a lag period and a decreased rate of thiobarbituric acid reactive product formation in the presence of individual lignans in combination with alpha-tocopherol suggesting recycling of alpha-tocopherol.

Topics: Animals; Antioxidants; Ascorbic Acid; Benzene Derivatives; Drug Synergism; Kinetics; Lignans; Lipid Peroxidation; Male; Microsomes, Liver; Mitochondria, Liver; Rats; Rats, Wistar; Sesamum; Structure-Activity Relationship; Thiobarbituric Acid Reactive Substances; Tocopherols; Vitamin E

The effect of CLA on paraoxonase 1 (PON1), one of the antioxidant proteins associated with HDL, was investigated for its protective action against oxidative inactivation as well as its stabilization activity. When cis-9 (c9),trans-11 (t11)-CLA and t10,c12-CLA were examined for their protective activity against ascorbate/Cu(2+)-induced inactivation of PON1 in the presence of Ca2+, two CLA isomers exhibited a remarkable protection (Emax, 71-74%) in a concentration-dependent manner (50% effective concentration, 3-4 microM), characterized by a saturation pattern. Such a protective action was also reproduced with oleic acid, but not linoleic acid. Rather, linoleic acid antagonized the protective action of CLA isomers in a noncompetitive fashion. Additionally, the two CLA isomers also protected PON1 from oxidative inactivation by H2O2 or cumene hydroperoxide. The concentration-dependent protective action of CLA against various oxidative inactivation systems suggests that the protective action of CLA isomers may be mediated through their selective binding to a specific binding site in a PON1 molecule. Separately, the inactivation of PON1 by p-hydroxymercuribenzoate (PHMB), a modifier of the cysteine residue, was also prevented by CLA isomers, suggesting the possible existence of the cysteine residue in the binding site of CLA. The c9,t11-CLA isomer seems to be somewhat more effective than t10,c12-CLA in protecting against the inactivation of PON1 by either peroxides or PHMB, in contrast to the similar efficacy of these two CLA isomers in preventing ascorbate/Cu(2+)-induced inactivation of PON1. Separately, CLA isomers successfully stabilized PON1, but not linoleic acid. These data suggest that the two CLA isomers may play a beneficial role in protecting PON1 from oxidative inactivation as well as in its stabilization.

Topics: Antioxidants; Aryldialkylphosphatase; Ascorbic Acid; Benzene Derivatives; Copper; Humans; Hydrogen Peroxide; Hydroxymercuribenzoates; Isomerism; Linoleic Acids, Conjugated; Oxidation-Reduction

Organic peroxides are widely used in the chemical industry as initiators of oxidation for the production of polymers and fiber-reinforced plastics, in the manufacture of polyester resin coatings, and pharmaceuticals. Free radical production is considered to be one of the key factors contributing to skin tumor promotion by organic peroxides. In vitro experiments have demonstrated metal-catalyzed formation of alkoxyl, alkyl, and aryl radicals in keratinocytes incubated with cumene hydroperoxide. The present study investigated in vivo free radical generation in lipid extracts of mouse skin exposed to cumene hydroperoxide. The electron spin resonance (ESR) spin-trapping technique was used to detect the formation of alpha-phenyl-N-tert-butylnitrone (PBN) radical adducts, following intradermal injection of 180 mg/kg PBN. It was found that 30 min after topical exposure, cumene hydroperoxide (12 mmol/kg) induced free radical generation in the skin of female Balb/c mice kept for 10 weeks on vitamin E-deficient diets. In contrast, hardly discernible radical adducts were detected when cumene hydroperoxide was applied to the skin of mice fed a vitamin E-sufficient diet. Importantly, total antioxidant reserve and levels of GSH, ascorbate, and vitamin E decreased 34%, 46.5%. 27%, and 98%, respectively, after mice were kept for 10 weeks on vitamin E-deficient diet. PBN adducts detected by ESR in vitamin E-deficient mice provide direct evidence for in vivo free radical generation in the skin after exposure to cumene hydroperoxide.

Topics: Administration, Cutaneous; Animals; Antioxidants; Ascorbic Acid; Benzene Derivatives; Biomarkers; Cyclic N-Oxides; Female; Free Radicals; Glutathione; Lipid Peroxidation; Mice; Mice, Inbred BALB C; Nitrogen Oxides; Oxidative Stress; Skin; Spin Labels; Spin Trapping; Sulfhydryl Compounds; Vitamin E; Vitamin E Deficiency

The antioxidant properties of S-nitrosoglutathione, a nitric oxide-derived product were studied in different experimental systems. By using the crocin bleaching test, S-nitrosoglutathione, in the presence of copper ions, shows an antioxidant capacity about six times higher than that of Trolox c and referable to the interception of peroxyl radicals by nitric oxide. Copper alone shows a modest inhibitory action, which is about seven times lower than that of Trolox c. S-nitrosoglutathione prevents lipid peroxidation induced by the well-known Fe2+/ascorbate system (IC50 = 450 microM) and the inhibitory effect is strongly reinforced by the presence of copper ions (IC50 = 6.5 microM). In addition, cumene hydroperoxide-induced lipid peroxidation is markedly decreased by S-nitrosoglutathione, provided that copper ions, maintained reduced by ascorbate, are present. Decomposition of S-nitrosoglutathione through metal catalysis and/or the presence of reducing agents and the consequent release of nitric oxide are of crucial importance for eliciting the antioxidant power. In this way, copper ions and/or reducing species with low antioxidant potency are able to promote the formation of an extremely strong antioxidant species such as nitric oxide.

Topics: Animals; Antioxidants; Ascorbic Acid; Benzene Derivatives; Carotenoids; Chromans; Copper; Ferrous Compounds; Lipid Peroxidation; Microsomes, Liver; Nitric Oxide; Peroxides; Rats; Reducing Agents; S-Nitrosoglutathione; Thiobarbituric Acid Reactive Substances

Probe-assisted flow cytometry was used to monitor the response of membranes of living cells to oxidant stress in the presence and absence of antioxidants. Test conditions (fluorophore loading, oxidant concentration) were investigated and storage-related changes in erythrocyte response to oxidant stress explored.. Erythrocytes were incubated with a lipophilic fluorescent probe and exposed to site-specific oxidant challenge, induced by cumene hydroperoxide, in the presence and absence of urate, ascorbate, or alpha tocopherol in physiological amounts. Fluorescence of labeled and treated erythrocytes was measured for 120 min using a Coulter EPICS Elite ESP flow cytometer.. Probe loading was dose and time dependent. Cumene hydroperoxide exhibited a potent and dose-dependent oxidant effect on erythrocyte membranes. Alpha tocopherol slowed, but did not prevent, membrane oxidation. Ascorbate appeared to have no effect on peroxidation initially, but then slowed and stopped propagation of membrane oxidation. The effect of urate was slight.. This technique can provide insight into oxidative processes at the cellular level. Results indicated that lipophilic alpha tocopherol was the most effective antioxidant in slowing membrane peroxidation, but ascorbate appears to stop chain propagation. This effect may be owing to vitamin C/E interaction. Further study is needed.

Topics: Antioxidants; Ascorbic Acid; Benzene Derivatives; Dose-Response Relationship, Drug; Erythrocyte Membrane; Flow Cytometry; Fluorescent Dyes; Humans; Lipid Peroxidation; Oxidative Stress; Time Factors; Uric Acid; Vitamin E

Induction of lipid peroxidation is shown to alter the structure of mitochondrial membrane and to activate endogenous phospholipases A2, C, D, and lysophospholipase A. Fe(2+)-, cumene hydroperoxide- and ultraviolet-induced lipid peroxidation results in the activation of mitochondrial phospholipases.

Topics: Animals; Ascorbic Acid; Benzene Derivatives; Calcium; Electron Spin Resonance Spectroscopy; Enzyme Activation; Intracellular Membranes; Isoenzymes; Lipid Peroxidation; Membrane Lipids; Membrane Proteins; Mitochondria, Liver; Oxidants; Phospholipases; Phospholipids; Rats; Ultraviolet Rays

The generation of free radicals by Cr(IV) from lipid hydroperoxides was investigated by ESR spin trapping. The spin trap used was 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Reaction of Cr(VI) with ascorbate was used as a source of Cr(IV). Incubation of Cr(VI) with ascorbate generated Cr(IV) and Cr(V). Addition of cumene hydroperoxide generated DMPO/R adduct with an enhancement of Cr(V) signal. Addition of Mn(II), whose function is to remove Cr(IV), caused dose-dependent inhibition of DMPO/R formation. Similar results were obtained using t-butyl hydroperoxide. Metal ion chelators, deferoxamine, 1,10-phenanthroline and diethylenetriaminepentaacetic acid inhibited DMPO/R formation in the order of deferoxamine > 1,10-phenanthroline > diethylenetriaminepentaacetic acid. The results suggest the possible role of Cr(IV) and its mediated free radical generation from lipid hydroperoxides in the mechanism of Cr(VI) carcinogenesis.

Topics: Ascorbic Acid; Benzene Derivatives; Chelating Agents; Chromium; Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Free Radicals; Lipid Peroxides; Manganese; Peroxides; Spin Labels; tert-Butylhydroperoxide

The one-electron reduction of vanadate (vanadium(V)) by ascorbate and related free radical generation at physiological pH was investigated by ESR and ESR spin trapping. The spin trap used was 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Incubation of vanadium(V) with ascorbate generated significant amounts of vanadium(IV) in phosphate buffer (pH 7.4) but not in sodium cacodylate buffer (pH 7.4) nor in water. The vanadium(IV) yield increased with increasing ascorbate concentration, reaching a maximum at a vanadium(V): ascorbate ratio of 2:1. Addition of formate to the incubation mixture containing vanadium(V), ascorbate, and phosphate generated carboxylate radical (.COO-), indicating the formation of reactive species in the vanadium(V) reduction mechanism. In the presence of H2O2 a mixture of vanadium(V), ascorbate, and phosphate buffer generated hydroxyl radical (.OH) via a Fenton-like reaction (vanadium(IV)+H2O2-->vanadium(V)+.OH+OH-). The .OH yield was favored at relatively low ascorbate concentrations. Omission of phosphate sharply reduced the .OH yield. The vanadium(IV) generated by ascorbate reduction of vanadium(V) in the presence of phosphate was also capable of generating lipid hydroperoxide-derived free radicals from cumene hydroperoxide, a model lipid hydroperoxide. Because of the ubiquitous presence of ascorbate in cellular system at relatively high concentrations, one-electron reduction of vanadium(V) by ascorbate together with phosphate may represent an important vanadium(V) reduction pathway in vivo. The resulting reactive species generated by vanadium(IV) from H2O2 and lipid hydroperoxide via a Fenton-like reaction may play a significant role in the mechanism of vanadium(V)-induced cellular injury.

Topics: Ascorbic Acid; Benzene Derivatives; Buffers; Electron Spin Resonance Spectroscopy; Free Radicals; Hydrogen-Ion Concentration; Hydroxyl Radical; Kinetics; Oxidation-Reduction; Phosphates; Vanadates

To elucidate the mechanism of cytotoxicity of H2O2, we selected H2O2-resistant Chinese hamster V79 cells by single-step selection from a pool of spontaneous variants. The resistant cells showed bimodal sensitivity to H2O2 without exhibiting a significantly higher level of the detoxicating enzymes, catalase, glutathione peroxidase and superoxide dismutase. Mode-one and mode-two killing were observed at lower (< 300 microM) and higher (> 2 mM) H2O2 concentrations, respectively. Mode-one but not mode-two killing was prevented by iron chelators. Pretreatment with low concentrations of ascorbic acid preferentially enhanced the killing at higher H2O2 concentrations. These resistant cells were cross-resistant to t-butyl hydroperoxide and cumene hydroperoxide.

Topics: Animals; Ascorbic Acid; Benzene Derivatives; Catalase; Cell Line; Cell Survival; Chelating Agents; Clone Cells; Cricetinae; Cricetulus; Deferoxamine; Dose-Response Relationship, Drug; Drug Resistance; Glucosephosphate Dehydrogenase; Glutathione Peroxidase; Hydrogen Peroxide; Kinetics; Peroxides; Phenanthrolines; Reactive Oxygen Species; Superoxide Dismutase; tert-Butylhydroperoxide

Topics: Adenosine Triphosphate; Animals; Antioxidants; Ascorbic Acid; Benzene Derivatives; Cromolyn Sodium; Cytidine Triphosphate; Female; Kinetics; Lipid Peroxidation; Male; Microsomes, Liver; Pentetic Acid; Rats; Uridine Triphosphate

Lipid peroxidation, as assessed by the formation of thiobarbituric acid substances on incubation with ascorbate-Fe2+, NADPH-ADP-Fe3+ and cumene hydroperoxide in brain homogenate and mitochondria, was significantly decreased during gestation and restored to respective control levels post partum. The decrease observed with the brain homogenate on Day 10 of pregnancy was 42% with ascorbate-Fe2+ and 70% with NADPH-ADP-Fe3+. This temporary decrease in peroxidation potential seems to be due to lesser availability of substrate in the form of unsaturated fatty acids besides increase in the cholesterol:phospholipid ratio and glutathione. Progesterone, the gestational steroid elaborated during pregnancy, inhibited lipid peroxidation in brain mitochondria in a dose-dependent manner. The observed temporary decrease in peroxidation potential may be a special adaptation to protect membranes in the brain against oxidant stress during pregnancy.

Topics: Adenosine Diphosphate; Animals; Ascorbic Acid; Benzene Derivatives; Brain Chemistry; Female; Lipid Peroxidation; Membrane Lipids; Mitochondria; NADP; Pregnancy; Pregnancy, Animal; Progesterone; Rats; Rats, Wistar; Thiobarbituric Acid Reactive Substances

cis-Parinaric acid (PnA) was used as a fluorescent probe to study lipid peroxidation in nonparasitized and Plasmodium falciparum-parasitized erythrocytes, upon challenge by cumene hydroperoxide and tert-butyl hydroperoxide. Parasitized erythrocytes were less susceptible toward lipid peroxidation than nonparasitized erythrocytes with which they had been cultured. Furthermore, nonparasitized erythrocytes cultured together with parasitized cells, and thereafter isolated on a Percoll gradient, were less susceptible toward lipid peroxidation than erythrocytes kept under the same experimental conditions but in the absence of parasitized cells. We concluded, therefore, that the intracellular development of the parasite leads to an increase in the resistance against oxidative stress, not only of the host cell membrane of the parasitized erythrocyte, but also in the plasma membrane of the neighboring cells. The erythrocyte cytosol of parasitized cells and/or the intraerythrocytic parasite was required for the increased protection of the host cell membrane, since ghosts prepared from parasitized erythrocytes were more susceptible to lipid peroxidation than those prepared from nonparasitized ones. Vitamin E content of parasitized erythrocytes was lower than that of nonparasitized cells. However, parasitized erythrocytes promoted extracellular reduction of ferricyanide at higher rates, which might be indicative of a larger cytosolic reductive capacity. It is suggested that the improved response of intact erythrocytes is due to an increased reduction potential of the host-erythrocyte cytosol. The role of vitamin C as a mediator of this process is discussed.

Topics: Animals; Ascorbic Acid; Benzene Derivatives; Cytosol; Erythrocyte Membrane; Erythrocytes; Fatty Acids, Unsaturated; Humans; In Vitro Techniques; Lipid Peroxidation; Oxidation-Reduction; Plasmodium falciparum; Vitamin E

Recently, we have described the ability of traditional lipid peroxidation inhibitors to inhibit ascorbate-stimulated collagen synthesis. In order to characterize further this effect, we have tested the ability of known and potential inhibitors of lipid peroxidation for their effects on ascorbate-stimulated collagen synthesis and lipid peroxidation. In our experiments, mannitol, a water soluble antioxidant, had no effect on ascorbate-induced collagen synthesis nor on lipid peroxidation. However, alpha-tocopherol, which is a lipophilic antioxidant, inhibited both effects of ascorbate. Superoxide dismutase, catalase, and their polyethylene glycol conjugate forms did not inhibit the ascorbate-stimulated collagen synthesis or lipid peroxidation. In addition, no effect was seen with the oxygen radical scavengers isopropanol, ethanol, or dimethyl sulfoxide. Two iron chelators, o-phenanthroline and alpha,alpha-dipyridyl, both inhibited ascorbate-induced lipid peroxidation and collagen synthesis, consistent with the previously described iron-dependence of lipid peroxidation by ascorbate. These results support a correlation between collagen synthesis and lipid peroxidation and provide a theory for the mechanism of ascorbic acid regulation of collagen synthesis.

Topics: Antioxidants; Ascorbic Acid; Benzene Derivatives; Cells, Cultured; Chelating Agents; Collagen; Free Radical Scavengers; Humans; Lipid Peroxidation

2,6-Diisopropylphenol (propofol), a new intravenous anaesthetic, has a structure similar to that of butylated hydroxytoluene (BHT). Both compounds inhibit the production of malondialdehyde (MDA) in rat liver mitochondria and microsomes as well as in rat brain synaptosomes treated with lipid peroxidation inducers.

Topics: Animals; Antioxidants; Ascorbic Acid; Benzene Derivatives; Brain Chemistry; Butylated Hydroxytoluene; Electron Transport; In Vitro Techniques; Iron; Lipid Peroxidation; Male; Malondialdehyde; Microsomes, Liver; Mitochondria, Liver; Propofol; Rats; Rats, Inbred Strains; Synaptosomes

Silybin has been complexed in 1:1 ratio with phosphatidyl choline to give IdB 1016 in order to increase its bioavailability. The antioxidant and free radical scavenger action of this new form of silybin has been evaluated. One hour after the intragastric administration to rats of IdB 1016 (1.5 g/kg b.wt.) the concentration of silybin in the liver microsomes was estimated to be around 2.5 micrograms/mg protein corresponding to a final concentration in the microsomal suspension used of about 10 microM. At these levels IdB decreased by about 40% the lipid peroxidation induced in microsomes by NADPH, CCl4 and cumene hydroperoxide, probably by acting on lipid derived radicals. Spin trapping experiments showed, in fact, that the complexed form of silybin was able to scavenge lipid dienyl radicals generated in the microsomal membranes. In addition, IdB 1016 was also found to interact with free radical intermediates produced during the metabolic activation of carbon tetrachloride and methylhydrazine. These effects indicate IdB 1016 as a potentially protective agent against free radical-mediated toxic damage.

Topics: Administration, Oral; Animals; Antioxidants; Ascorbic Acid; Benzene Derivatives; Carbon Tetrachloride; Cytochrome P-450 Enzyme System; Free Radicals; Iron; Lipid Peroxidation; Male; Malondialdehyde; Microsomes, Liver; NADH Dehydrogenase; NADP; Oxidation-Reduction; Phosphatidylcholines; Rats; Rats, Inbred Strains; Silymarin

Simultaneous addition of ascorbic acid and organic hydroperoxides to rat liver microsomes resulted in enhanced lipid peroxidation (approximately threefold) relative to incubation of organic hydroperoxides with microsomes alone. No lipid peroxidation was evident in incubations of ascorbate alone with microsomes. The stimulatory effect of ascorbate on linoleic acid hydroperoxide (LAHP)-dependent peroxidation was evident at all times whereas stimulation of cumene hydroperoxide (CHP)-dependent peroxidation occurred after a lag phase of up to 20 min. EDTA did not inhibit CHP-dependent lipid peroxidation but completely abolished ascorbate enhancement of lipid peroxidation. Likewise, EDTA did not significantly inhibit peroxidation by LAHP but dramatically reduced ascorbate enhancement of lipid peroxidation. The results reveal a synergistic prooxidant effect of ascorbic acid on hydroperoxide-dependent lipid peroxidation. The inhibitory effect of EDTA on enhanced peroxidation suggests a possible role for endogenous metals mobilized by hydroperoxide-dependent oxidations of microsomal components.

Topics: Animals; Ascorbic Acid; Benzene Derivatives; Edetic Acid; Iron; Kinetics; Linoleic Acids; Lipid Peroxidation; Lipid Peroxides; Male; Microsomes, Liver; Rats; Rats, Inbred F344; Thermodynamics

The influence of deciduoma-induced differentiation on the lipid peroxidation in the rat uterus was investigated. The wet weight of uterus and its protein content increased during deciduoma progression. Content of the thiobarbituric acid reactive substances (TBARS) as well as lipid peroxidation induced by ascorbate and cumene hydroperoxide showed significant decreases during deciduoma growth. Restoration of normalcy was observed during regression. The activity of superoxide dismutase, an inhibitor of lipid peroxidation showed an opposite pattern namely increase during deciduoma development and decline during the regressive phase. We conclude that cell differentiation during deciduoma induction is accompanied by a temporary and reversible decrease in the peroxidative potential of the rat uterus.

Topics: Animals; Ascorbic Acid; Benzene Derivatives; Cell Differentiation; Decidua; Female; Lipid Peroxidation; Organ Size; Pregnancy; Rats; Rats, Inbred Strains; Thiobarbiturates; Uterus

Rough and smooth microsomes of brain in senescent rats showed less sensitivity to ascorbate-, NADPH- and cumene hydroperoxide-induced peroxidative damage compared with those of young adults. The observed decrease in peroxidative potential in senescent rats seemed to be due to decrease in the substrate for peroxidation in the form of phospholipids and increase in the level of antioxidants such as reduced glutathione and superoxide dismutase.

Topics: Aging; Animals; Ascorbic Acid; Benzene Derivatives; Brain; Glutathione; Lipid Peroxidation; Male; Malondialdehyde; Microsomes; NADP; NADPH-Ferrihemoprotein Reductase; Oxidation-Reduction; Phospholipids; Rats; Rats, Inbred Strains; Superoxide Dismutase

Topics: Acetaminophen; Animals; Ascorbic Acid; Benzene Derivatives; Cytochrome P-450 Enzyme System; Horseradish Peroxidase; In Vitro Techniques; Microsomes, Liver; NADP; Oxidation-Reduction; Peroxides; Prostaglandin-Endoperoxide Synthases; Rats; Rats, Inbred Strains

The antioxidative potential of cyanobacteria to scavenge hydroperoxides formed as by-products of photosynthetic activity was investigated in Nostoc muscorum 7119 and Synechococcus 6311. These cells contained a high concentration of glutathione, 2-5 mM, and a low concentration of ascorbate, 20-100 uM. No glutathione peroxidase was detected while the activity of ascorbate peroxidase was high, reacting with hydrogen peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Dehydroascorbate reductase was active in recycling ascorbate and glutathione reductase regenerated glutathione from glutathione disulphide. The activity of these antioxidative enzymes in the cyanobacteria was sufficient to remove between 60-230 nmoles H2O2 .mg protein-1 min-1. It is suggested that in cyanobacteria an effective reaction sequence for removal of hydroperoxides involves ascorbate peroxidase and recycling of glutathione and ascorbate.

Topics: Ascorbate Peroxidases; Ascorbic Acid; Benzene Derivatives; Cyanobacteria; Glutathione; Glutathione Peroxidase; Oxidation-Reduction; Oxidoreductases; Peroxidases; Peroxides; Photosynthesis; Selenium

The antioxidant effect of alpha-tocopherolquinone and alpha-tocopherolhydroquinone was studied in liposomes and rat liver submitochondrial particles. Both alpha-tocopherolquinone and alpha-tocopherolhydroquinone inhibit lipid peroxidation induced by ascorbate/Fe2+ in liposomes and by cumene hydroperoxide in submitochondrial particles. Alpha-tocopherolhydroquinone is much more effective than alpha-tocopherolquinone in inhibiting lipid peroxidation. Submitochondrial particles, depleted of ubiquinones and reincorporated with alpha-tocopherolquinone, are protected from lipid peroxidation only in the presence of succinate. Alpha-tocopherolquinone cannot replace endogenous ubiquinones in the respiratory chain function, nevertheless it can be reduced by the mitochondrial respiratory chain substrates, presumably through the reduced ubiquinones.

Topics: alpha-Tocopherol; Animals; Ascorbic Acid; Benzene Derivatives; Cattle; Electron Transport; Ferrous Compounds; Lipid Peroxides; Liposomes; Malondialdehyde; Mitochondria, Liver; Oxidation-Reduction; Rats; Submitochondrial Particles; Succinates; Succinic Acid; Ubiquinone; Vitamin E

Irradiation with u.v. light of aerobic aqueous media containing both rabbit liver microsomal fraction and 4-chloroaniline results in N-oxidation of the arylamine. The reaction is severely blocked by exhaustive extraction with organic solvents of the microsomal membranes to remove lipids. Further, scavengers of OH. and O2.-impair the photochemical process. These findings suggest that the observed phenomenon may be closely associated with light-induced lipid peroxidation. Indeed, N-oxidation of 4-chloroaniline is fully preserved when either phospholipid liposomes or dispersed linoleic acid substitute for intact microsomal fraction. Co-oxidation of the amine substrate occurs during iron/ascorbate-promoted lipid peroxidation also, but H2O2 or free OH. radicals do not appear to be involved. Cumene hydroperoxide-sustained rabbit liver microsomal turnover of the amine generates N-oxy product via O2-dependent and -independent pathways; propagation of lipid peroxidation is presumed to govern the former route. Lipid hydroperoxides, either exogenously added to rabbit liver microsomal suspensions or enzymically formed from arachidonic acid in ram seminal-vesicle microsomal preparations, support N-oxidation of 4-chloroaniline. The significance, in arylamine activation, of lipid peroxidation in certain extrahepatic tissues exhibiting but low mono-oxygenase activity is discussed.

Topics: Aniline Compounds; Animals; Ascorbic Acid; Benzene Derivatives; Female; In Vitro Techniques; Light; Lipid Metabolism; Lipid Peroxides; Liposomes; Male; Microsomes, Liver; Oxidation-Reduction; Rabbits