摘要:

PhenylN-tert-butyl nitrone (PBN) is commonly employed in spin-trapping studies. We report here evidence that PBN in aqueous solutions is decomposed by two pathways leading to the generation of nitric oxide ('NO). The first pathway is by hydrolysis of PBN, which is strongly catalyzed by ferric iron. The second pathway is via PBN-hydroxyl radical adduct formation. NO was trapped in the presence of cysteine and ferrous iron to form a [(cys)2Fe(NO)2]−3complex, which was measured by use of electron paramagnetic resonance (EPR) spectroscopy. A concomitant metabolite, benzaldehyde, was detected from both reaction mixtures. We propose that PBN is hydrolyzed by Fe3+or attacked by hydroxyl radical, leading eventually to a common transient species,tert-butyl hydronitroxide [t-BuN(O')H], which is further oxidized to a 'NO source,t-BuNO. Our data imply that PBN may decompose to 'NO when used in biological models with oxidative stress conditions.

ISSN:1071-5762    

DOI:10.3109/10715769509064014

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The spin traps substituted with some groups at the 4-position of dimethyl-1-pyrroline N-oxide(DMPO) were compared with DMPO itself regarding their abilities as spin traps and their physical properties. 4,5,5-Trimethyl-l-pyroHine N-oxide (4MDMPO) and 5,5-dimethyl- 4-phenyl-l-pyrolline N-oxide (4PDMPO) were synthesized by the Bonnett method, and 5,5-dimethyl-4-hydroxymethyl-l-pyrolline N-oxide (4HMDMPO) was made by a unique method from 2(5H)-furanone. The melting points of 4MDMPO, 4PDMPO and 4HMDMPO were higher than that of DMPO. The magnitude of hydrophilicity was in the order of 4HMDMPO, DMPO, 4MDMPO, and 4PDMPO based on the partition coefficient experiments in a 1-octanol–water system. Several radicals, O2, HO-, -CH3, -CH2OH, -CH(CH3)OH, (CH3)3CO and H radicals, were trapped with these DMPO derivatives for comparison with the trapping by DMPO itself. Spin adducts of O J with the three DMPO derivatives showed ESR spectra similar to that of DMPO. In spite of the formation of diastereomers arising from spin trapping, the line-width enlargement was very small. The intensities and the decay rates of the spectra of 4MDMPO-O2−, 4PDMPO-O2−4HMDMPO-O2−and DMPO-O2−were almost equal. In the trapping of the OH radical by 4MDMPO, 4PDMPO and 4HMDMPO, the eight-line ESR spectra observed were different from the well-known four-line spectrum of DMPO-OH.

ISSN:1071-5762    

DOI:10.3109/10715769509064015

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

We have examined free radical production in a rat model of focal cerebral ischemia using microdialysis coupled with EPR analysis. A microdialysis probe was inserted 2 mm into the cerebral cortex, supplied by the right middle cerebral artery (MCA), and after a 2-hour washout period with artificial cerebral spinal fluid (ACSF), the perfusate solution was changed to ACSF containing the spin trapping agent, 5,5-dimethyl-1-pyrroline N-oxide (DMPO). No free radicals were detected by DMPO during the pre-ischemia period. Both common carotid arteries and the right MCA were then ligated for 90 minutes. Microdialysate collected every 15 min during the ischemic period demonstrated predominantly superoxide or peroxyl radical production. After release of the occlusive sutures, hydroxyl radical became apparent initially, then thiyl and carbon centered radicals appeared later in samples collected every 15 min for two hours following cortical reperfusion. Careful studies on the purification and stability of DMPO solution were performed to circumvent artifacts and spurious signals.

ISSN:1071-5762    

DOI:10.3109/10715769509064016

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The effects of intravenous administration of a-phenyl N-tert-butyl nitrone (PBN) on cortical cerebral blood flow (CBF) were examined in Wistar rats under pentobarbital anesthesia and artificial ventilation. The cortical CBF in parietal cortex was measured by laser Doppler flowmetry. Intravenous administrations of 2 mg/kg and 20 mg/kg of PBN dose-dependently produced significant increases in cortical CBF and decreases in systemic blood pressure (BP). To examine whether these increased responses in cortical CBF produced by PBN were associated with the vasodilatation system of nitric oxide (NO), the NO synthase inhibitor L-NG-nitroarginine (L-NOArg), which is an analog of L-arginine, was used to inhibit the NO-related-vasodilatative system. Since the PBN-induced responses in the cortical CBF were much attenuated in L-NOArg-treated rats (30 mg/kg, iv.), it was inferred that NO-related vasodilatation was strongly associated with the PBN-induced increase in cortical CBF.

ISSN:1071-5762    

DOI:10.3109/10715769509064017

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Luteoskyrin is a hepatotoxic and hepatocarcinogenic bisdihydroanthraquinone produced byPenicillium islandicumSopp. By observing the EPR spectra of DMPO-spin adducts and luteoskyrin semiquinone radical, we investigatedin vitrowhether luteoskyrin is reduced to its semiquinone radical leading to the generation of active oxygen species in redox systems catalyzed by NADPH-dependent cytochrome reductases of the liver. We found (1) the formation of luteoskyrin semiquinone radical in the NADPH-cytochrome P-450 reductase system under anaerobic conditions, (2) the generation of O−in the systems composed of luteoskyrin, NAD(P)H, and either rat liver microsomal NADPH-cytochrome P-450 reductase or submitochondrial particles and (3) dicoumarol showed no effect on the O−generation in the case of submitochondrial particles. From these results we proposed that luteoskyrin liver injuries are induced by the active oxygen species generated in the process of autoxidation of luteoskyrin semiquinone radical which is produced in the one-electron redox systems catalyzed by the liver NAD(P)H-dependent cytochrome reductases.

ISSN:1071-5762    

DOI:10.3109/10715769509064018

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Using ESR with 5,5-dimethyl-l-pyrroline N-oxide (DMPO) as a spin-trapping reagent, we measured the levels of free radical species generated from living cells ofChlorella vulgarisvar.vulgails(IAM C-534). To investigate the production of free radicals in the livingChlorella vulgariscells, the influence of DMPO toward the intact cells of theChlorella vulgarisusing the O2evolution rate was first studied as a guide. Since the 02evolution rate was not changed by DMPO, it was judged that DMPO has no toxicity toward the intact cells ofChlorella vulgaris.Only hydroxyl radicals (-OH) were detected as the DMPO-OH adduct in the suspension of intact cells ofChlorella vulgarisirradiated with visible light. Moreover, since production of -OH was inhibited by some hydroxyl radical scavengers such as KI and ethanol, production of -OH was proved to be due to hydroxyl radicals. It was also clear that the intensity of OH increased with increasing irradiation intensity of visible light. Therefore, it was suggested that -OH might be one of the photoinhibition factors of the intactChlorella vulgariscells in severe light conditions.

ISSN:1071-5762    

DOI:10.3109/10715769509064019

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Paraquat is a synthetic bipyridylium salt widely used as herbicide and defoliant. Enzyme-catalyzed redox-cycling of paraquat generates oxygen radicals. The toxic, even lethal, effects of paraquat are due to free radical-mediated tissue injury. Ocular lesions, sometimes quite severe, have been observed following accidental splashing of paraquat solutions onto the eyes.These studies were designed to document the generation of paraquat free radicals in corneal tissue, and to describe the histological nature of the corneal injuries in experimental animals (rabbits and monkeys). The EPR spectrum of rabbit corneas, 30 min. after intrastromal injection of paraquat, showed the signal of the free radical of paraquat. Ultrastructural studies of corneas 8 days after intrastromal injections (100μl) of paraquat solutions showed that the initial lesions occur at the epithelium/basement membrane interface. In rabbit cornea, dose dependent lesions were observed, i.e. whereas 50 mM paraquat caused only minimal damage to the epithelial basement membrane, 75 mM caused complete dissolution to the basement membrane with some damage to stromal collagen, and loss of epithelium with stromal ulceration and severe inflammatory response were observed with 150 mM paraquat. Monkey corneas were less susceptible than those of rabbits to the effects of paraquat. No lesions were observed following intrastromal injections of 50 mM or 75 mM paraquat. With higher concentrations of paraquat (100 mM and 150 mM) the primary injuries were to the proximal and lateral plasma membranes of basal epithelial cells; basement membrane alterations were detected only adjacent to areas of significant plasma membrane damage. The underlying Bowman's membrane and stroma were not affected. Anatomical differences between the corneas of rabbit and monkeys as well as possible biochemical differences may account for the species differences observed.

ISSN:1071-5762    

DOI:10.3109/10715769509064020

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Polymorphonuclear leukocytes (PMNs) have been suggested to be damaged by superoxide radical generated on their own. The protective capacity of a spin trapping compound, phenyl-N-tert-butyl nitrone (PBN) was evaluated for this damage which occurs after the induction of superoxide generation. The life span of PMNs after superoxide generation was measured in the presence of PBN using the cell counting method, and effects of PBN on the amount of superoxide generated were quantitated using both cytochrome c reduction and spin trapping with DMPO. Results indicated significant extension of life span when PBN was present, and the extension was dose dependent. However, the magnitude of life span extension was not as large as expected from the decrease of superoxide generation. Possible mechanisms for the protection of PMNs by PBN are discussed.

ISSN:1071-5762    

DOI:10.3109/10715769509064021

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Adriamycin (ADR)-induced cardiotoxicity was adopted in this investigation as a reliable model of radical-dependent myocardial pathology allowing both quantitative studies of drug activity in the isolated organ andin vivocomparison of the cardio-protection vs. general toxicity. Since commercially available lipophilic spin trapping compounds were shown to develop significant protective activity, in this investigation a newly synthesized spin trap (2-phenyl-DMPO) was studied. In Langendorff rat heart, 200μM ADR induced a significant impairment of contractile performance, while 2-phenyl-DMPO was not cardiotoxic up to the 5 mM concentration. By this dose, 2-phenyl-DMPO induced a significant protection against the ADR-induced contractile impairment. Inin vivoexperiments, ADR (9 mg/kg i. v.) produced a significant impairment of ECG, coronary flow and contractility. The continuous administration of 2-phenyl-DMPO i.p. by osmotic pump delivering 0.3,μmol/hr was unable to protect the animals against the cardiotoxic signs. Seven days after ADR administration, severe general toxicity (arrest of body weight increase) and myelotoxicity were also observed. 2-phenyl-DMPO was unable to protect the animals from these toxic signs. The present results confirm that lipophilic spin traps can be a new class of antiradical drugs, as confirmed by the experiments performed in the isolated heart with the 2-phenyl-DMPO; however, this last compound is probably metabolizedin vivoto inactive derivatives.

ISSN:1071-5762    

DOI:10.3109/10715769509064022

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

ISSN:1071-5762    

DOI:10.3109/10715769509064023

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor