甲基莲心碱对电解性氧自由基损伤离体大鼠心脏的保护作用

甲基莲心碱（Ｎｅｆ）显著降低电解性氧自由基损伤离体大鼠心脏所致室性心律失常发生率，减少心肌细胞中乳酸脱氢酶的释放及丙二醛的生成．对氧自由基所致的冠脉流量减少，左室内压（ＬＶＰ）及±ｄＰ／ｄｔｍａｘ的降低亦具有对抗作用。我们推测甲基莲心碱对电解性氧自由基损伤离体大鼠心脏的保护作用可能与其清除活性氧自由基及抑制脂质过氧化作用有关。     

Ischemia-reperfusion injury and histamine release in isolated guinea-pig heart: the role of free radicals

Free radicals produced by the occlusion and opening of the left anterior descending coronary artery and/or by perfusion of isolated guinea-pig heart with FeCl3/ADP (10 microM/100 microM) induce a differential release of histamine and lactate dehydrogenase (LDH) in the perfusates with a preferential liberation of histamine in the reperfusion phase, associated with an increase of ventricular arrhythmias. The release of histamine has been correlated with malonyldialdehyde (MDA) production and tissue calcium content in left ventricular tissue. MDA increased during ischemia, while the calcium content increased when the tissue was reperfused. Under these conditions, N-t-butyl-alpha-phenylnitrone (BPN), a molecule capable of forming spin adducts with free radicals, and D-mannitol are active in preventing reperfusion-induced arrhythmias.     

Lysophosphatidylcholine-induced arrhythmias and its accumulation in the rat perfused heart.

1. The tissue level of lysophosphatidylcholine (LPC) was determined in rat hearts perfused with a solution containing 5 microM LPC. The relationship between LPC accumulation and the severity of arrhythmias produced was examined. 2. The accumulation of LPC was dependent on the perfusion time and this accumulation was associated with the occurrence of severe arrhythmias. A positive correlation between the tissue LPC content and the arrhythmia score was found (P less than 0.01). 3. No consistent alteration in total phospholipid, phosphatidylcholine or cholesterol content was found. This suggests that LPC-induced arrhythmias are not associated with alterations of major lipid components in the heart. 4. When severe arrhythmias occurred in the presence of LPC in the rat perfused heart, less than 2% of total tissue phospholipid was in the form of LPC. 5. The positive correlation between LPC accumulation and the occurrence of arrhythmias suggests a cause and effect relationship of LPC with cardiac arrhythmias in the rat perfused heart. However, in the ischaemic heart, other biochemical factors can contribute, to different degrees, to ischaemia-induced cardiac arrhythmias.     

Creatine phosphate and protection against reperfusion-induced arrhythmias in the rat heart

An isolated perfused working rat heart preparation was used to assess the effect of including creatine phosphate (10 mmol/l) in the perfusion fluid of hearts subjected to aerobic perfusion (20 min), regional ischaemia (15 min) and reperfusion (2 min). Creatine phosphate had no detectable effect upon pre-ischaemic, ischaemic or post-ischaemic contractile function, it also had no statistically significant effect upon myocardial tissue ATP content. However, creatine phosphate was found to afford striking protection against reperfusion-induced arrhythmias. The incidence of ventricular fibrillation was reduced from over 80% (13/16) in the control group to 10% in the creatine phosphate-treated group (P less than 0.001). Possible mechanisms underlying the anti-arrhythmic effects of creatine phosphate were investigated using isolated rat papillary muscles superfused with or without added creatine phosphate (10 mmol/l). During aerobic superfusion at 37 degrees C creatine phosphate did not cause any statistically significant changes in contractile (developed tension) or electrophysiological (dV/dtmax and action potential duration) indices. Creatine phosphate did however influence the extent to which hypoxia (10 min) and reoxygenation (10 min) altered tension and electrophysiological characteristics. It accelerated the hypoxia-induced decline in developed tension and also the reoxygenation-induced recovery of developed tension. Relatively small changes in dV/dtmax and action potential duration were observed during hypoxia and these rapidly normalized during reoxygenation. In general creatine phosphate acted to exacerbate any changes during hypoxia and accelerate the recovery during reoxygenation. While some of the electrophysiological changes observed would indicate an anti-arrhythmic effect, they were relatively small and perhaps insufficient to explain fully the potent anti-arrhythmic properties of creatine phosphate.     

Prophylactic effects of m-nisoldipine and nisoldipine on reperfusion arrhythmias exacerbated by free radical generating system in Langendorff heart of rat

Xanthine-xanthine oxidase (X-XOD, 500 mumol/L + 100 nmol/L) free radical generating system was perfused 10 min prior to coronary artery ligation until the end of the experiment. It exacerbated the reperfusion ventricular fibrillation, reduced the activities of superoxide dismutase and catalase and increased the contents of malondialdehyde in Langendorff heart of rats. m-Nisoldipine or nisoldipine (0.05 mumol/L) was perfused 10 min prior to coronary artery ligation until the end of the experiment. They prevented reperfusion arrhythmias exacerbated by X-XOD and decreased the free radicals generated by X-XOD.     

Role of maltol in advanced glycation end products and free radicals: in-vitro and in-vivo studies

Inhibitors of advanced glycation end products (AGEs) have potential as preventive agents against diabetic complications. In-vitro AGE inhibitory activity, transition metal chelating, and free radical scavenging activity tests have been used to screen for and identify effective AGE inhibitors. In an ongoing project to elucidate AGE inhibiting active components of heat-processed ginseng, maltol was selected for more detailed investigation. Although there are several lines of evidence concerning the antioxidant activity of maltol, the in-vitro and in-vivo inhibitory effects of maltol on AGE generation have not been evaluated. In the present study, the in-vitro AGE inhibitory effects and free radical scavenging activity of maltol were investigated. In addition, the in-vivo therapeutic potential of maltol against diabetic renal damage was tested using streptozotocin (STZ)-diabetic rats. Maltol showed a stronger AGE inhibitory effect than aminoguanidine, a well known AGE inhibitor. In addition, the hydroxyl radical scavenging activity of maltol on electron spin resonance (ESR) spectrometry was slightly stronger than that of aminoguanidine. Therefore, maltol was found to have stronger in-vitro AGE inhibiting activity compared with aminoguanidine. The administration of 50 mgkg(-1) per day of maltol suppressed the elevated serum levels of glycosylated protein, renal fluorescent AGEs, carboxymethyllysine, receptors for AGEs, and nuclear factor-kappaB p65 in diabetic control rats. These beneficial effects of maltol against STZ-diabetic renal damage were thought to result from its free radical scavenging and AGE inhibitory effects.     

Oxygen free radicals and the penis

Penile erection is dependent upon vascular smooth muscle relaxation in erectile tissue and penile arteries, the principal mediator of relaxation being nitric oxide (NO). Evidence from basic scientific studies indicates that oxidative stress mediated through the superoxide radical (superoxide) and other reactive oxygen species (ROS) may be central to impaired cavernosal function in erectile dysfunction (ED). Increased inactivation of NO by superoxide results in impaired penile NO transmission and smooth muscle relaxation. Furthermore, propagation of endothelial dysfunction by ROS may result in chronic impairment of penile vascular function, a process analogous to early atherogenesis. Indeed, ED and atherosclerosis are closely linked through shared risk factors. Given our current understanding of ED pathophysiology, antioxidants may be of benefit in both the short- and long-term. Evidence supporting the paradigm of antioxidant therapy for the prevention or treatment of ED is presented herein.     

Oxygen free radicals and the penis

Penile erection is dependent upon vascular smooth muscle relaxation in erectile tissue and penile arteries, the principal mediator of relaxation being nitric oxide (NO). Evidence from basic scientific studies indicates that oxidative stress mediated through the superoxide radical (superoxide) and other reactive oxygen species (ROS) may be central to impaired cavernosal function in erectile dysfunction (ED). Increased inactivation of NO by superoxide results in impaired penile NO transmission and smooth muscle relaxation. Furthermore, propagation of endothelial dysfunction by ROS may result in chronic impairment of penile vascular function, a process analogous to early atherogenesis. Indeed, ED and atherosclerosis are closely linked through shared risk factors. Given our current understanding of ED pathophysiology, antioxidants may be of benefit in both the short- and long-term. Evidence supporting the paradigm of antioxidant therapy for the prevention or treatment of ED is presented herein.     

Pharmacological and biochemical studies on the role of free radicals during stress-induced immunomodulation in rats

The present study was designed to evaluate the role of free radicals in restraint stress (RS)-induced modulation of immune responses in rats. RS significantly suppressed both humoral and cell-mediated immune responses as evidenced by reduced (a) anti-SRBC antibody titre (b) splenic Plaque Forming Cell counts, (c) footpad thickness response, and (d) IFN-γ and IL-4 levels. Assay for oxidative stress markers in blood showed that there was significant enhancement in plasma corticosterone and products of lipid peroxidation, viz. malondialdehyde and lowered reduced glutathione levels on exposure to RS. Further, this was associated with decreased antioxidant enzyme activity, viz. superoxide dismutase and catalase. These RS-induced changes in immunological and oxidative stress markers were markedly attenuated by pretreatment with the antioxidants, l-ascorbic acid (100 and 200 mg/kg) and α-tocopherol (30 and 60 mg/kg), by differential degrees. The combination of l-ascorbic acid and α-tocopherol was shown to have synergistic effects on reversal of these RS-induced effects. The results suggest that reactive oxygen species may be involved in stress-induced immunomodulation.     

Free radicals and oxidative stress: targeted ESR measurement of free radicals

The detection of free radicals generated within the body may contribute to clarifying the pathophysiological role of free radicals in disease processes. As an appropriate procedure to examine the generation of free radicals in a biological system, electron spin resonance (ESR) has emerged as a powerful tool for detection and identification. A method for determination of oxygen radical scavenging activity using ESR and the spin trapping technique was developed. Oxygen radicals were trapped by 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) or alpha-phenyl-N-t-butylnitrone (PBN), and the DMPO or PBN spin adduct signal was measured quantitatively by an ESR spectrometer. The spin trapping method using ESR has also been reported for not only in vitro and ex vivo measurements but also in vivo measurements. In in vivo ESR, nitroxyl radical is being used as a spin trap well. ESR signal intensities of nitroxyl radical are measured after administration to animals and the signal decay rates of nitroxyl radical have reported to be influenced by various types of oxidative stress. With this method, it is possible to specify the type of radical or the location at which the free radicals are produced. The spin trapping method by in vivo ESR is an effective procedure for giving non-invasive measurements in animals. ESR imaging in the organs of live animals can also be obtained after injection of nitroxyl radicals as an imaging agent using ESR-computed tomography. In vivo ESR imaging has been established as a powerful technique for determining the spatial distribution of free radicals in living organs and tissues.     

Oxidation of ethanol to acetaldehyde and free radicals by rat testicular microsomes

A large number of epidemiological studies evidencing that excessive alcohol consumption is associated with impaired testosterone production and testicular atrophy are available in the literature. One hypothesis to explain the deleterious action of alcohol involves the in situ biotransformation to acetaldehyde, but it strongly suggests the need to learn more about the enzymatic processes governing alcohol metabolism to acetaldehyde in different cellular fractions since limited information is available in the literature. In this article we report studies on the metabolic conversion of alcohol to acetaldehyde and to 1-hydroxyethyl radicals in rat testicular microsomal fractions. The oxidation of ethanol to acetaldehyde in rat testes microsomal fraction was mostly of enzymatic nature and strongly dependent on the presence of NADPH and oxygen. Several compounds were able to significantly decrease the production of acetaldehyde: SKF 525A; diethyldithiocarbamate; esculetin; gossypol; curcumin; quercetin; dapsone; and diphenyleneiodonium. Microsomal preparations in the presence of NADPH were also able to produce both hydroxyl and 1-hydroxyethyl free radicals. Their generation was modulated by the presence of diphenyleneiodonium, gossypol, and deferoxamine. Results show that rat microsomal fractions are able to metabolize alcohol to deleterious chemicals, such as acetaldehyde and free radicals, that may be involved in ethanol toxic effects. Enzymes involved could include CYP2E1, P450 reductase, and other enzymes having lipoxygenase- /peroxidase-like behavior.     

槲皮素对在体大鼠心肌缺血再灌性心律失常的保护作用

本文用在体Wistar大鼠心肌缺血再灌注模型,观察槲皮素对缺血再灌性心律失常的保护作用。在再灌前1min至再灌后2min静脉滴注槲皮素(0.5mmol/L,10ml/kg),可显著缩短心律失常的持续时间,降低室颤的发生率、再灌注区心肌组织中MDA的含量及XOD的活性,而对SOD具有明显的保护作用。结果提示槲皮素的抗心肌缺血再灌性心律失常作用可能与抑制心肌组织中OFR的形成和保护心肌组织中SOD或直接清除OFR有关。     

Role of free radicals in the mechanisms of hemolysis and lipid peroxidation by silica: comparative ESR and cytotoxicity studies

Electron spin resonance (ESR) and cytotoxicity measurements were made on newly fractured silica to examine specifically the role of the fracture-induced, silicon-based radicals (Si. and SiO.) and silica-generated hydroxyl (.OH) radicals in the mechanism of the cell membrane damage by silica. The concentration of the Si. and SiO. radicals was controlled through decay processes, thermal annealing, and boiling, while that of the .OH radicals was varied by using catalase, superoxide dismutase, KMnO4, Na2SeO3, ascorbic acid, and metal ions, and monitored via ESR spectroscopy. The dust's cytotoxicity potential was evaluated by measuring the silica-induced hemolysis and also by determining lipid peroxidation (using linoleic acid). From the comparison of hemolysis and ESR results it is deduced that the radicals play little or no role in the silica-induced hemolysis. However, the lipid peroxidation data indicate that the radicals might be involved in the initiation of an oxidative chain reaction leading to the macrophage membrane damage through lipid peroxidation.     

Biochemical and ultrastructural evidences for toxicity of lead through free radicals in rat brain

Studies suggest that some lead-induced toxic effects may occur through free radical production and oxidative stress. This study examined the relationship between brain histopathological alterations and oxidative stress in subchronic lead exposure. Male Albino rats received lead acetate at 0.01%, 0.05% and 0.1% w/v in their drinking water for 30 days. Animals given sodium acetate (0.1% w/v) served as control in the same period. At the end of exposure, blood-lead levels, blood catalase (CAT) and superoxide dismutase (SOD) activities and malondialdehyde (MDA) content (in blood and brain) were measured. The brain tissue samples were prepared and analysed by light and scanning electron microscopy. The results show that, the blood-lead levels in treated animals were higher in comparison with control. CAT and SOD activities in animals treated with 0.01% and 0.05% w/v did not increase in comparison with control (P > 0.05) but these values were higher in animals treated with 0.1% w/v lead acetate (P < 0.01). MDA content in blood and brain of animals treated with lead acetate 0.1% w/v, increased significantly (P <0.01), but these values were not significantly increased in other treated animals. No major histopathological alterations were detected in the brains of animals treated with lead acetate at 0.01% and 0.05% w/v. In animals treated with lead acetate 0.1% w/v, demyelinization and collagenous scar formation with neuronal atrophy in hippocampus region was observed. It is concluded that lead acetate induce oxidative stress which has an important role in brain damage in rats.     

卡托普利与谷胱甘肽清除氧自由基的比较研究

用化学发光方法比较研究了卡托普利（Ｃａｐ）和谷胱甘肽（ＧＳＨ）抗氧自由基的作用。结果表明，Ｃａｐ和ＧＳＨ都具有相似的基本结构一取代的Ｎ－羧甲基－β－巯基丙酰胺。两者对黄嘌呤－黄嘌呤氧化酶体系以及碱性连苯三酚自氧化体系产生的都有清除作用并具量效关系．Ｃａｐ比ＧＳＨ的清除作用大。两者对Ｈ２Ｏ２的清除作用的量效关系曲线十分相似。结果提示．Ｃａｐ具有ＧＳＨ相似的抗氧自由基作用．并且有取代的Ｎ－羧甲基－β－巯基丙酰胺这种结构特征的化合物，也可能具有ＧＳＨ样的作用。     

Histamine release by free radicals: the relationship with the signal transduction system

In isolated rat serosal mast cells exposed to free radical-generating systems, the release of histamine was associated with a significant increase in malonyldialdehyde (MDA) production suggesting a relationship between histamine release and membrane lipid peroxidation. Under these circumstances, an increase in cytosolic calcium was observed, uncoupled with any stimulation of inositol phospholipid (PtdIns) breakdown. The data suggest similarities between the release of histamine induced by calcium ionophores and by free radical-generating systems.     

EPR studies of free radicals decay and survival in gamma irradiated aminoglycoside antibiotics: sisomicin, tobramycin and paromomycin

Radiation sterilization technology is more actively used now that any time because of its many advantages. Gamma radiation has high penetrating power, relatively low chemical reactivity and causes small temperature rise. But on the other hand radiosterilization can lead to radiolytic products appearing, in example free radicals. Free radicals in radiative sterilized sisomicin, tobramycin and paromomycin were studied by electron paramagnetic resonance (EPR) spectroscopy. Dose of gamma irradiation of 25kGy was used. Concentrations and properties of free radicals in irradiated antibiotics were studied. EPR spectra were recorded for samples stored in air and argon. For gamma irradiated antibiotics strong EPR lines were recorded. One- and two-exponential functions were fitted to experimental points during testing and researching of time influence of the antibiotics storage to studied parameters of EPR lines. Our study of free radicals in radiosterilized antibiotics indicates the need for characterization of medicinal substances prior to sterilization process using EPR values. We propose the concentration of free radicals and other spectroscopic parameters as useful factors to select the optimal type of sterilization for the individual drug. The important parameters are i.a. the τ time constants and K constants of exponential functions. Time constants τ give us information about the speed of free radicals concentration decrease in radiated medicinal substances. The constant K(0) shows the free radicals concentration in irradiated medicament after long time of storage.     

Environmentally persistent free radicals inhibit cytochrome P450 activity in rat liver microsomes

Combustion processes generate particulate matter that affects human health. When incineration fuels include components that are highly enriched in aromatic hydrocarbons (especially halogenated varieties) and redox-active metals, ultrafine particulate matter containing air-stable, environmentally persistent free radicals (EPFRs) is generated. The exposure to fine EPFRs (less than 2.5 μm in diameter) has been shown to negatively influence pulmonary and cardiovascular functions in living organisms. The goal of this study was to determine if these EPFRs have a direct effect on cytochrome P450 function. This was accomplished by direct addition of the EPFRs to rat liver microsomal preparations and measurement of several P450 activities using form-selective substrates. The EPFRs used in this study were formed by heating vapors from an organic compound (either monochlorophenol (MCP230) or 1,2-dichlorobenzene (DCB230)) and 5% copper oxide supported on silica (approximately 0.2 μm in diameter) to 230 °C under vacuum. Both types of EPFRs (but not silica, physisorbed silica, or silica impregnated with copper oxide) dramatically inhibited the activities of CYP1A, CYP2B, CYP2E1, CYP2D2 and CYP3A when incubated at concentrations less than 0.1 mg/ml with microsomes and NADPH. Interestingly, at the same concentrations, the EPFRs did not inhibit HO-1 activity or the reduction of cytochrome c by NADPH-cytochrome P450 reductase. CYP2D2-selective metabolism by rat liver microsomes was examined in more detail. The inhibition of CYP2D2-selective metabolism by both DCB230- and MCP230-EPFRs appeared to be largely noncompetitive and was attenuated in the presence of catalase suggesting that reactive oxygen species may be involved in the mechanism of inhibition.