摘要:

RRR-alpha-Tocopherol (Vitamin E) was assayed in plasma of 48 patients with viral hepatitis and of 32 healthy controls. In patients with highly elevated serum transaminases (ALT<100 U/L) vitamin E plasma levels were significantly lower (17.5±4.8μmol/L) than in controls (22.7±4.2μmol/L, p<0.01). The vitamin E/ lipid ratios (3.12±0.63μmol/g) in these patients were 33% lower than those of the controls (4.68±0.54μmol/g). The lowered vitamin E levels in patients with acute or chronic viral hepatitis with high activity of disease may be due to free radical-mediated liver injury.

ISSN:1071-5762    

DOI:10.3109/10715769609149068

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Hydroxyl and 1-hydroxyethyl radical adducts of 5, 5-dimethylpyrroline N-oxide (DMPO) were prepared by photolysis, and mechanisms for loss of their EPR signals in rat liver microsomal suspensions were evaluated. Rates of NADPH-dependent EPR signal loss were more rapid in phosphate buffer than in Tris buffer. Addition of superoxide dismutase (SOD) partially protected the adducts when Tris was used as a buffer, but was relatively ineffective in the presence of phosphate. The ferrous iron chelator bathophenanthrolene partially protected the spin adducts in the presence and absence of phosphate, but complete protection was observed when SOD was also added. The spin adducts were unstable in the presence of Fe+2and K3Fe(CN)6, but Fe+3alone had little effect on the EPR signals. The data are consistent with two mechanisms for microsomal degradation of DMPO spin adducts under these conditions. Microsomes form superoxide in the presence of oxygen and NADPH, which attacks these DMPO spin adducts directly. The spin adducts are also degraded in the presence of Fe+2, and phosphate stimulates this iron-dependent destruction of DMPO spin adducts.

ISSN:1071-5762    

DOI:10.3109/10715769609149069

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Fischer 344 rats were injected with the spin traps C-phenyl N-tert-butyl nitrone (PBN, 150 mg/kg bw,ip) or 4-pyridine-N-oxide N-tert-butyl nitrone (POBN, 775 mg/kg bw,ip), and exposed to clean air or 2 ppm ozone for two hours. The presence of spin adducts was determined by electron paramagnetic resonance (EPR) spectroscopy of chloroform extracts of lung and liver homogenates. No significant levels of adducts were detected in the lungs of air control animals. Benzoyl N-tert-butyl aminoxyl, attributed to direct reaction of ozone with PBN, andtert-butyl hydroaminoxyl, the scission product of the hydroxyl adduct of PBN, were detected in the lungs of ozone exposed rats. EPR signals for carbon-centred alkoxyl and alkyl adducts were also detected with PBN in the lungs and liver of animals exposed to ozone. With POBN, only carbon-centred alkyl radicals were detected. Senescent, 24 months old rats were found to retain about twice more14C-PBN in blood, heart and lungs by comparison to juvenile, 2 months old animals. Accordingly, the EPR signals were generally stronger in the lungs of the senescent rats by comparison to juvenile rats. Together, the observations were consistent with the previously proposed notion that a significant flux of hydrogen peroxide produced from the reaction of ozone with lipids of the extracellular lining, or from activated macrophages in the lungs could be a source of biologically relevant amounts of hydroxyl radical.

ISSN:1071-5762    

DOI:10.3109/10715769609149070

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Effect of nitric oxide (NO) on the respiratory burst of neutrophils was examined under different oxygen tensions. Phorbol myristate acetate (PMA) stimulated oxygen consumption and superoxide (O2-) generation in neutrophils by a mechanism which was inhibited reversibly by NO. The inhibitory effect of NO increased significantly with a decrease in oxygen tension in the medium. The inhibitory effect of NO was suppressed in medium containing oxyhemoglobin (HbO2), a NO scavenging agent. In contrast, 3-morpholinosydnonimine (SIN-1), a compound that rapidly generates peroxynitrite (ONOO-) from the released NO and O2-, slightly stimulated the PMA-induced respiratory burst. These results suggested that NO, but not ONOO, might reversibly inhibit superoxide generation by neutrophils especially at physiologically low oxygen tensions thereby decreasing oxygen toxicity particularly in and around hypoxic tissues.

ISSN:1071-5762    

DOI:10.3109/10715769609149071

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

The toxicity of ozone, the major component of photochemical smog, is related to its powerful oxidising ability, and many of its deleterious effects are mediated through free radical reactions. As the majority of ozone oxidation events are thought to be confined to the pulmonary epithelial lining fluid, we studied the interaction of ozone with a range of small molecular weight antioxidants found within this compartment: ascorbic acid (AH2), uric acid (UA), and reduced glutathione (GSH). Epithelial lining fluid obtained as bronchoalveolar lavage (BAL) fluid, was taken from 16 male subjects and the antioxidant concentrations determined for each subject. BAL fluid samples from nine of these subjects were then exposed, using an interfacial exposure system, to a range (50-1000 ppb) of ozone concentrations. Both AH2and UA were consumed by ozone in a time and ozone concentration dependent manner, with mean consumption rates of 1.7±0.8 and 1.0±0.5 pmol L-1s-1ppb-1, respectively. Considerable intersubject variation was however observed. The individual rates of consumption for each antioxidant were significantly correlated with the respective initial antioxidant concentration. In contrast, although GSH was consumed at 50 ppb ozone, the rate of consumption did not change with increasing ozone concentration. We conclude that there is differential depletion of BAL fluid antioxidants, suggesting a reactivity hierarchy toward ozone in human ELF of AH2>UA±GSH.

ISSN:1071-5762    

DOI:10.3109/10715769609149072

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Phenoxyl radicals generated by laser flash photolysis were found to react withβ-carotene with concomitantβ-carotene bleaching in two parallel reactions with similar rates: (i) formation of aβ-carotene adduct with a (pseudo) first order rate constant of 1-1.5±104s-1with absorption maximum around 800 nm, and (ii) formation of aβ-carotene radical cation with a (pseudo) first order rate constant of 2-3±104s-1with absorption maximum around 920 nm. Bothβ-carotene radicals decay on a similar time scale and have virtually disappeared after 100 ms, theβ-carotene adduct by a second order process. Oxygen had no effect onβ-carotene bleaching or radical formation and decay. The reduction of phenoxyl radicals byβ-carotene may prove important for an understanding of howβ-carotene acts as an antioxidant.

ISSN:1071-5762    

DOI:10.3109/10715769609149073

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Lipid peroxidation (LPO) of polyunsaturated fatty acids (PUFAs) is suspected to be involved in the generation of chronic diseases. A model reaction for LPO is the air oxidation of PUFAs initiated by Fe2+and ascorbic acid. In the course of such model reactions glycolaldehyde (GLA) was detected as main aldehydic product. Since it is difficult to explain the generation of GLA by oxidation of PUFAs, it was suspected that GLA might be derived by oxidation of ascorbic acid. This assumption was verified by treatment of ascorbic acid with Fe2+.Produced aldehydic compounds were trapped by addition of pentafluorobenzylhydroxylamine hydrochloride (PFBHA-HCl), trimethylsilylated and finally identified by gas chromatography/mass spectrometry (GC/MS). Oxidation of ascorbic acid with O2in presence of iron ions produced not only glycolaldehyde (GLA), but also glyceraldehyde (GA), dihydroxyacetone (DA) and formaldehyde. Glyoxal (GO) and malondialdehyde (MDA) were detected as trace compounds.The yield of the aldehydic compounds was increased by addition of lipid hydroperoxides (LOOH) or H2O2. The buffer influenced the reaction considerably: Iron ions react with Tris buffer by producing dihydroxyace-tone (DA). Since ascorbic acid is present in biological systems and Fe2+ions are obviously generated by cell damaging processes, the production of GLA and other aldehydic components might add to the damaging effects of LPO.Glucose suffers also oxidation to short-chain aldehydic compounds in aqueous solution, but this reaction requires addition of equimolar amounts of Fe2+together with equimolar amounts of H2O2or 13-hydroperoxy-9-cis-11-trans-octadecadienoic acid (13-HPODE). Therefore this reaction, also influenced by the buffer system, seems to be not of biological relevance.

ISSN:1071-5762    

DOI:10.3109/10715769609149074

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

A method to determine Mn-superoxide dismutase activity by measuring directly the rate of decay of O2-in a spectrophotometer, is described. Decay of O2-generated by KO2at pH 9.5, was monitored as the fall in absorbance (A250nm-A360nm). Mn-superoxide dismutase was determined as the activity of cyanide-resistant superoxide dismutase, calculated from the rate of O2-dismutation. Mn-superoxide dismutase could be determined in the presence of a 700 times higher Cu, Zn-superoxide dismutase activity. The alkaline pH did not cause analytical problems. The assay was used to measure both Mn- and Cu, Zn-superoxide dismutase activity in mitochondrial preparations. The assay had a detection limit of 2.8 ng/ml when Mn-superoxide dismutase from E. coli was used, and the between-day CV was 5.8%. The assay is an alternative to indirect methods for detecting superoxide dismutase activity.

ISSN:1071-5762    

DOI:10.3109/10715769609149075

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor