RESUMEN
RESUMEN Introducción: las enfermedades cardiovasculares actualmente son la principal causa de muerte en los países industrializados y se espera que también lo sean en los países en vías de desarrollo en el año 2020. Entre ellas la enfermedad arterial coronaria es la manifestación más prevalente, y se asocia a alta morbimortalidad. La ateroesclerosis es su principal génesis y por tanto los trastornos del metabolismo de los lípidos. Objetivo: determinar el perfil lipídico en pacientes egresados por síndrome coronario agudo. Materiales y métodos: se realizó una investigación descriptiva, transversal, correlacional en los pacientes egresados del servicio de cardiología del hospital Faustino Pérez en el período comprendido entre enero y diciembre del 2015. Resultados: se observó un aumento de los lípidos colesterol, triglicéridos, LDL-c, VLDL y Lp (a) en más del 50% de los pacientes estudiados. Los índices de Apo B/Apo A y Col/HDL-c marcaron como indicador de alto riesgo en un 67,5 y 58,75 % respectivamente. La HDL-c considerada como factor protector, resultó disminuida en más del 50% de los pacientes. Conclusiones: se detectó correlación entre el síndrome coronario agudo y trastornos en el metabolismo de los lípidos. Se recomienda realizar estudios observacionales epidemiológicos para determinar la verdadera influencia de estos factores como agente causal de síndrome coronario agudo (AU).
ABSTRACT Introduction: Currently, cardiovascular diseases are the main cause of death in developed countries, and it is believed that they also will be the same in developing countries in 2020 year. Among them, coronary arterial disease is the most prevalent manifestation, and is associated to high morbi-mortality. Atherosclerosis is its most important cause and consequently the disorders of the lipids metabolism. Objective: determining the lipid profile in patients discharged for acute coronary syndrome. Materials and methods: a descriptive, cross-sectional, correlational research was carried out in patients discharged from the service of Cardiology of the hospital Faustino Perez in the period from January to December 2015. Results: it was found an increase of the lipids cholesterol, triglycerides, LDL-c, VLDL and Lp(a) in more than 50 % of the studied patients. The indexes of Apo B/Apo A and Col/HDL-c were high risk indicators in 67.5 and 58.75 % respectively. HDL-c, considered as a protecting factor, was diminished in more than 50 % of the patients. Conclusions: a correlation was found between the acute coronary syndrome and disturbances in the lipids metabolism. We recommend performing epidemiologic, observational studies to determine the real influence of these factors as causal agent of the acute coronary syndrome (AU).
Asunto(s)
Humanos , Enfermedades Cardiovasculares , Factores de Riesgo , Morbilidad , Síndrome Coronario Agudo/epidemiología , Lípidos/análisis , Enfermedad de la Arteria Coronaria , Cardiología , Epidemiología Descriptiva , Estudios Transversales , Prevención de Enfermedades , Radicales Libres/sangre , Correlación de Datos , Estilo de VidaRESUMEN
RESUMEN Introducción: las enfermedades cardiovasculares actualmente son la principal causa de muerte en los países industrializados y se espera que también lo sean en los países en vías de desarrollo en el año 2020. Entre ellas la enfermedad arterial coronaria es la manifestación más prevalente, y se asocia a alta morbimortalidad. La ateroesclerosis es su principal génesis y por tanto los trastornos del metabolismo de los lípidos. Objetivo: determinar el perfil lipídico en pacientes egresados por síndrome coronario agudo. Materiales y métodos: se realizó una investigación descriptiva, transversal, correlacional en los pacientes egresados del servicio de cardiología del hospital Faustino Pérez en el período comprendido entre enero y diciembre del 2015. Resultados: se observó un aumento de los lípidos colesterol, triglicéridos, LDL-c, VLDL y Lp (a) en más del 50% de los pacientes estudiados. Los índices de Apo B/Apo A y Col/HDL-c marcaron como indicador de alto riesgo en un 67,5 y 58,75 % respectivamente. La HDL-c considerada como factor protector, resultó disminuida en más del 50% de los pacientes. Conclusiones: se detectó correlación entre el síndrome coronario agudo y trastornos en el metabolismo de los lípidos. Se recomienda realizar estudios observacionales epidemiológicos para determinar la verdadera influencia de estos factores como agente causal de síndrome coronario agudo (AU).
ABSTRACT Introduction: Currently, cardiovascular diseases are the main cause of death in developed countries, and it is believed that they also will be the same in developing countries in 2020 year. Among them, coronary arterial disease is the most prevalent manifestation, and is associated to high morbi-mortality. Atherosclerosis is its most important cause and consequently the disorders of the lipids metabolism. Objective: determining the lipid profile in patients discharged for acute coronary syndrome. Materials and methods: a descriptive, cross-sectional, correlational research was carried out in patients discharged from the service of Cardiology of the hospital Faustino Perez in the period from January to December 2015. Results: it was found an increase of the lipids cholesterol, triglycerides, LDL-c, VLDL and Lp(a) in more than 50 % of the studied patients. The indexes of Apo B/Apo A and Col/HDL-c were high risk indicators in 67.5 and 58.75 % respectively. HDL-c, considered as a protecting factor, was diminished in more than 50 % of the patients. Conclusions: a correlation was found between the acute coronary syndrome and disturbances in the lipids metabolism. We recommend performing epidemiologic, observational studies to determine the real influence of these factors as causal agent of the acute coronary syndrome (AU).
Asunto(s)
Humanos , Enfermedades Cardiovasculares , Factores de Riesgo , Morbilidad , Síndrome Coronario Agudo/epidemiología , Lípidos/análisis , Enfermedad de la Arteria Coronaria , Cardiología , Epidemiología Descriptiva , Estudios Transversales , Prevención de Enfermedades , Radicales Libres/sangre , Correlación de Datos , Estilo de VidaRESUMEN
Toxoplasma gondii is a cosmopolitan protozoan that causes disease in several species, including humans. In cats, these infections are usually asymptomatic, but in other species they can lead to high levels of inflammatory and cell damage markers, causing cellular damage. Therefore, the aim of this study was to measure levels of tumor necrosis factor (TNF-α), reactive oxygen species (ROS), and nitric oxide (nitrite/nitrate-NOx) in the serum of cats seropositive for T. gondii. Initially, we investigated the presence of antibodies against T. gondii in cats in the city of Concordia, Santa Catarina, Brazil, with the use of indirect immunofluorescence (IFA), and found 30 cats seropositive for T. gondii and 30 seronegative cats. In this study, seropositive cats showed higher levels of TNF-α, ROS, and NOx compared to seronegative cats. Although cats do not show clinical signs of disease, constant inflammatory response can cause cell damage, which over time may adversely affect the animal.
Asunto(s)
Enfermedades de los Gatos/metabolismo , Radicales Libres/sangre , Óxido Nítrico/sangre , Toxoplasmosis Animal/metabolismo , Factor de Necrosis Tumoral alfa/sangre , Animales , Anticuerpos Antiprotozoarios/sangre , Enfermedades Asintomáticas , Enfermedades de los Gatos/sangre , Enfermedades de los Gatos/inmunología , Gatos , Ensayo de Inmunoadsorción Enzimática/veterinaria , Técnica del Anticuerpo Fluorescente Indirecta/veterinaria , Especies Reactivas de Oxígeno/sangre , Espectrofotometría/veterinaria , Toxoplasmosis Animal/sangre , Toxoplasmosis Animal/inmunologíaRESUMEN
Tuberculosis (TB) is one of the most common infectious diseases in the world. Mycobacterium tuberculosis infection leads to pulmonary active disease in approximately 5-10% of exposed individuals. Both bacteria- and host-related characteristics influence latent infection and disease. Host genetic predisposition to develop TB may involve multiple genes and their polymorphisms. It was reported previously that interferon gamma (IFN-γ) and nitric oxide synthase 2 (NOS2) are expressed on alveolar macrophages from TB patients and are responsible for bacilli control; thus, we aimed this study at genotyping single nucleotide polymorphisms IFNG+874T/A SNP and NOS2A-954G/C SNP to estimate their role on TB susceptibility and determine whether these polymorphisms influence serum nitrite and NOx(-) production. This case-control study enrolled 172 TB patients and 179 healthy controls. Neither polymorphism was associated with susceptibility to TB. NOS2A-954G/C SNP was not associated with serum levels of nitrite and NOx(-). These results indicate that variants of IFNG+874T/A SNP and NOS2A-954G/C SNP do not influence TB susceptibility or the secretion of nitric oxide radicals in the study population.
Asunto(s)
Estudios de Asociación Genética , Interferón gamma/genética , Óxido Nítrico/sangre , Tuberculosis/genética , Adulto , Brasil , Estudios de Casos y Controles , Femenino , Radicales Libres/sangre , Predisposición Genética a la Enfermedad , Genética de Población , Humanos , Masculino , Persona de Mediana Edad , Óxido Nítrico/genética , Óxido Nítrico Sintasa de Tipo II/genética , Polimorfismo de Nucleótido Simple , Tuberculosis/sangre , Tuberculosis/patologíaRESUMEN
O objetivo deste estudo foi analisar a influência da crioimersão corporal (CIC) imediata ao esforço físico agudo no estresse oxidativo (EOx) no plasma sanguíneo. Participaram do presente estudo 12 homens, com idade média de 22±1 anos, submetidos ao teste de esforço físico intenso em esteira, seguido de CIC em um tanque com água a 10ºC durante 10 minutos contínuos. Do repouso ao final da CIC, os indivíduos foram monitorados através de alguns parâmetros como: o índice de percepção subjetiva do esforço (IPE) expresso conforme escala de Borg, frequência cardíaca (FC), pressão arterial (PA) e temperatura corporal (TC) através da temperatura timpânica. A análise morfológica do EOx plasmático foi realizada de acordo com o método denominado Morfologia Óptica do Estresse Oxidativo no Plasma (MEOP), utilizando-se gotas de sangue capilar. Observou-se uma significativa elevação (p<0,01) no grau do estresse oxidativo plasmático após a realização do esforço físico, em relação ao respectivo grau em repouso. Porém, esta elevação no grau do EOx foi significativamente reduzida (p<0,001) em função da CIC. Embora sejam necessários mais estudos científicos com o MEOP, concluiu-se que, para o presente estudo, este teste mostrou-se viável. Os dados encontrados no presente estudo sugerem que a CIC em água a 10ºC por 10 minutos imediatos ao esforço físico agudo com intensidade alta, apresenta-se como uma importante conduta fisioterapêutica para a normalização do EOx pós-esforço.
The purpose of this study was to analyze the influence of cold water immersion (CWI) following acute physical exercise on the oxidative stress in the blood plasma. Twelve men with average age of 22±1 years old, participated this study. All of them underwent the treadmill stress test followed by CWI in tank with water at 10ºC for 10 minutes. During this process, they were monitored and a set of parameters were analyzed: physical effort perception (Borg Scale), Heart Rate (HR), Blood Pressure (BP) and body heat, by measuring tympanic temperature. The morphological analysis of oxidative stress in blood plasma was done in accordance with a method known as Optical Morphology of the Oxidative Stress on Blood Plasma, which uses drops of capillary blood. A significant increase (p<0.01) in the rate of oxidative stress in plasma was noted after intense physical effort when compared with the rate of stress while at rest. However, the stress rate was significantly decreased (p<0.001) after CWI. Although further scientific studies should be carried out on the above mentioned test, may be concluded that, in the present study, the test has proven itself viable. The data found in the present study suggest that cold water immersion at 10ºC for 10 minutes following high intensity physical effort appears to be an important physical therapeutic measure towards the normalization of oxidative stress.
Asunto(s)
Humanos , Masculino , Adulto , Crioterapia , Inmersión , Estrés Oxidativo , Esfuerzo Físico , Plasma , Radicales Libres/sangreRESUMEN
Phenylketonuria (PKU) is the most frequent disturbance of amino acid metabolism being caused by severe deficiency of phenylalanine hydroxylase activity. Untreated PKU patients present severe mental retardation whose pathophysiology is not completely estabilished. Despite the low-Phe diet, a considerable number of phenylketonuric patients present a mild to moderate psychomotor delay and decreased cognitive functions. In the present study we evaluated various parameters of oxidative stress namely thiobarbituric acid-reactive species (TBA-RS), total antioxidant reactivity (TAR) and activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in two groups of treated PKU patients, one with well controlled and the other with high Phe blood levels in order to investigate whether blood Phe concentrations could be correlated with the extend of oxidative stress. We initially verified a marked increase of TBA-RS, and a decrease of TAR in plasma, as well as a reduction of erythrocyte GSH-Px activity which were similar in both groups of PKU patients, when compared to controls of similar ages. In contrast, CAT and SOD activities were not altered in PKU patients. These results show that oxidative stress occurs in PKU patients and that this pathogenic process is probably not directly correlated to Phe blood levels.
Asunto(s)
Estrés Oxidativo , Fenilcetonurias/dietoterapia , Fenilcetonurias/metabolismo , Catalasa/metabolismo , Niño , Eritrocitos/enzimología , Radicales Libres/sangre , Glutatión Peroxidasa/metabolismo , Humanos , Peroxidación de Lípido , Fenilalanina/sangre , Superóxido Dismutasa/metabolismo , Sustancias Reactivas al Ácido Tiobarbitúrico/metabolismoRESUMEN
Maple syrup urine disease (MSUD) or branched-chain alpha-keto aciduria (BCKA) is an inherited disorder caused by a deficiency of the branched-chain alpha-keto acid dehydrogenase complex (BCKAD) activity. The blockage of this pathway leads to tissue accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine and valine and their respective keto-acids. The clinical features presented by MSUD patients include ketoacidosis, convulsions, coma, psychomotor delay and mental retardation. The mechanism of brain damage in this disease is still poorly understood. However, an increase in lipid peroxidation in vitro in cerebral cortex of young rats as well as a decrease in the antioxidant defenses has been previously observed. In the present work we evaluated different oxidative stress parameters, named reactive species of thiobarbituric acid (TBARS), total antioxidant reactivity (TAR) and total antioxidant status (TAS) in plasma of MSUD patients in order to evaluate whether oxidative stress is involved in this disorder. We verified a marked increase of plasma TBARS measurements, which is indicative of increased lipid peroxidation, as well as a decrease on plasma TAR reflecting a deficient capacity to efficiently modulate the damage associated with an increased production of reactive species. In contrast, TAS was not changed indicating that the total content of antioxidants in plasma of patients affected by MSUD was not altered. These results suggest that free radical generation is elicited in MSUD and is possibly involved in the pathophysiology of the tissue damage found in this disorder.
Asunto(s)
Antioxidantes/metabolismo , Peroxidación de Lípido , Enfermedad de la Orina de Jarabe de Arce/metabolismo , Estrés Oxidativo , Proteínas Sanguíneas/metabolismo , Radicales Libres/sangre , Humanos , Lactante , Recién Nacido , Sustancias Reactivas al Ácido Tiobarbitúrico/metabolismoRESUMEN
A hanseniase e uma doença infecciosa cronica causada pelo mycobacterium leprae com um amplo espectro clinico e imunopatologico. Entre os mecanismos de defesa devenvolvidos pelo hospedeiro esta a geração de radicais livres, os quais promovem a destruição do bacilo. Os radicais livres são produzidos dentro das celulas por reaçoes endogeneas, geralmente oxidativas, que ocorrem em processos metabolicos normais, e temabem em condições anormais, como na inflamação causada por doença infecciosas. Este trabalho visa estudar a atividade de substâncias antioxidantes e sua relação com o estresse oxidativo gerado na resposta à hanseniase. Foram realizados experimentos com as enzimas superoxido dismutase(SOD) e catalase(CAT), além do antioxidantes glutationa(GSH) e a participação de óxido nitrico(NO) como indicador da presença de radicais livres. Os resultados foram comparados com um grupo controle e aqueles de pacientes sem tratamento e em tratamento com PQT. Os resultados obtidos indicam um aumento de até 280 por cento dos niveis dos antioxidantes, bem como dos metabolitos do oxido nitrico (596 por cento) em relação ao controle, sugerindo estresse oxidativo severo nos pacientes hansenianos. Os pacientes em tratamento mostram um aumento de até 87 por cento nos niveis de antioxidantes comparados ao controle, reduzindo a geração de radicais livres em relação aos individuos sem tratamento. Portanto, a medida do balanço entre defesas antioxidantes e a presença de radicais livres pode ser uma excelente ferramenta de estudo dos niveis de estresse oxidativo e sua contribuição na evolução da hanseniase.
Asunto(s)
Humanos , Estrés Oxidativo/fisiología , Lepra/epidemiología , Lepra/fisiopatología , Lepra/rehabilitación , Radicales Libres/análisis , Radicales Libres/sangre , Radicales Libres/síntesis químicaRESUMEN
Hypercholesterolemia is linked to endothelial dysfunction and enhancement of the endogenous inhibitor of NO synthase. The statins have lipid-lowering and pleiotropic properties, which could exert protective effects on the endothelium in hypercholesterolemia. The association of L-arginine with simvastatin could promote a further improvement on endothelial function in this condition. Thus, we investigated whether simvastatin, with or without supplementation with L-arginine, could improve endothelium-dependent vasodilation. In this study, 25 hypercholesterolemic subjects were treated according to the following protocol: washout period of 1 month; simvastatin (20 mg/day) for 2 months; simvastatin (20 mg/day) + L-arginine (7 g/day) for 2 months. From these patients, 10 were chosen at random for evaluation of vascular function by high resolution ultrasonography of the brachial artery. In subjects treated with simvastatin plus L-arginine, an increase of L-arginine levels (68%) and L-arginine/asymmetric dimethylarginine (ADMA) ratio (67%) were observed. Simvastatin reduced the plasma concentrations of NO metabolites nitrite + nitrate (NOx: 34%), S-nitrosothiols (RSNO: 42%), total cholesterol (25%), low density lipoprotein (LDL)-cholesterol (36%) and the LDL-cholesterol/high density lipoprotein (HDL-cholesterol ratio (34%). Simvastatin, associated or not to L-arginine, did not affect ADMA levels and endothelium-dependent vasodilation. Our data showed that simvastatin reduced the plasma concentrations of NOx and RSNO without affecting either the levels of ADMA or endothelium-dependent vasodilation in hypercholesterolemia.
Asunto(s)
Arginina/análogos & derivados , Arginina/sangre , Arginina/uso terapéutico , Hipercolesterolemia/sangre , Óxido Nítrico/metabolismo , Simvastatina/uso terapéutico , Vasodilatación/efectos de los fármacos , Anticolesterolemiantes/farmacología , Anticolesterolemiantes/uso terapéutico , Arginina/farmacología , Relación Dosis-Respuesta a Droga , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/fisiopatología , Femenino , Radicales Libres/sangre , Humanos , Hipercolesterolemia/tratamiento farmacológico , Hipercolesterolemia/fisiopatología , Lípidos/sangre , Masculino , Persona de Mediana Edad , Nitratos/sangre , Óxido Nítrico/sangre , Óxido Nítrico Sintasa/antagonistas & inhibidores , Óxido Nítrico Sintasa/sangre , Nitritos/sangre , S-Nitrosotioles/sangre , Simvastatina/farmacología , Factores de TiempoRESUMEN
Peroxynitrite, which is formed by the fast reaction between nitric oxide and superoxide anion, has been receiving increasing attention as a mediator of human diseases. An initial controversy about the possibility of free radical production from peroxynitrite in test tubes has been resolved, and presently it is important to establish whether peroxynitrite produces radicals in cells. Here we employed the EPR spin trapping methodology with 5,5-dimethylpyrroline N-oxide (DMPO) to study the interaction of peroxynitrite with human erythrocytes. The results confirmed previous findings in demonstrating that oxyhemoglobin is the main target of peroxynitrite in erythrocytes. As we first show here, the produced ferryl-hemoglobin oxidizes its own amino acids and, most probably, amino acids from other hemoglobin monomers to produce hemoglobin-tyrosyl and hemoglobin-cysteinyl radicals. In parallel, ferryl-hemoglobin also oxidizes intracellular glutathione to produce the glutathiyl radical. The EPR spectrum of both DMPO/(*)cysteinyl-hemoglobin (a(beta)(H) = 15.4 G) and DMPO/(*)tyrosyl-hemoglobin (a(beta)(H) = 8.8 G) radical adducts was characterized. It is proposed that erythrocytes can be efficient peroxynitrite scavengers in vivo through the coupled action of oxyhemoglobin and glutathione. Overall, the results indicate that, through the intermediacy of carbon dioxide and/or hemoproteins, oxidation of glutathione to the glutathiyl radical is likely to be an important consequence of peroxynitrite production in vivo.
Asunto(s)
Cisteína/sangre , Eritrocitos/metabolismo , Glutatión/sangre , Hemoglobinas/metabolismo , Oxidantes/sangre , Ácido Peroxinitroso/sangre , Óxidos N-Cíclicos/sangre , Espectroscopía de Resonancia por Spin del Electrón/métodos , Radicales Libres/sangre , Radicales Libres/metabolismo , Glutatión/biosíntesis , Hemoglobinas/biosíntesis , Humanos , Oxidación-Reducción , Marcadores de Spin , Tirosina/sangreRESUMEN
Oxidative stress has been developed using dietary carbonyl-iron and iron-dextran parenteral administration as models of in vivo iron overload in rats. Carbonyl-iron led to a 2-fold increase in plasma iron content, a significant decrease (34%) in ascorbate plasma content and non-significant changes in plasma ascorbyl radical content. Iron-dextran produced a dramatic increase (6.7-fold) in plasma iron content, overwhelming the plasma total iron binding capacity. The ascorbyl radical content increased significantly in iron-dextran treatment (2.6-fold) and plasma ascorbate level was not affected. Ascorbyl radical/ascorbate ratio was significantly higher in both iron treated groups as compared with the control group (4 x 10(-4)+/-1 x 10(-4)). Data reported here indicate that the ascorbyl radical/ascorbate ratio is an appropriate in vivo indicator of oxidative stress under conditions of iron overload. The overall mechanism that describes the ascorbate status in plasma seems to be strongly dependent on the way the excess of iron is stored and thus, to the availability of the catalytically active iron for interacting with the plasma components. On this regard, evaluation of A*/AH(-) ratio did not help to discriminate between the possible involved mechanisms.
Asunto(s)
Antioxidantes/metabolismo , Ácido Ascórbico/sangre , Sobrecarga de Hierro/sangre , Estrés Oxidativo/fisiología , Animales , Biomarcadores , Espectroscopía de Resonancia por Spin del Electrón , Radicales Libres/sangre , Hierro/sangre , Masculino , Ratas , Ratas Wistar , Sustancias Reactivas al Ácido Tiobarbitúrico/metabolismoRESUMEN
Malondialdehyde [MDA] is a major end product of lipid peroxidation which causes tissue damage and its presence is often used as an indicator for free radical damage in tissues. MDA was therefore measured in the urine and plasma of 15 non-insulin dependent diabetics (NIDDM) between the ages of 33 and 67 (mean 52) years, 10 chronic smokers 29 - 33 years old and control group of 14 healthy individuals 17 to52 years old. The average age of both the normal controls and smokers was 32 years with an average Body Metabolic Index (BMI) of 24 in both groups and 26 in the diabetic group. (A table showing mean + SEM values for urinary and plasma malondialdehyde is shown in abstract). We conclude that diabetics and smokers have significantly (p<0.008) higher levels of urinary MDA than the controls. Plasma MDA levels were only significantly higher for the diabetic group. When corrected for muscle mass and BMI, urinary MDA levels for the two test groups were sigificantly (p<0.001) higher than normal. There was a good correlation between urinary MDA and plasma MDA (r=0.74), p<0.001, df= 21. These data suggest (1) NIDM and smokers have increased exposure to free radical damage (2) urinary MDA provides a good indicator of lipid peroxidation. (AU)
Asunto(s)
Adulto , Humanos , Malondialdehído/sangre , Malondialdehído/orina , Radicales Libres/sangre , Radicales Libres/orina , Diabetes Mellitus Tipo 2/fisiopatología , Tabaquismo/fisiopatología , Peroxidación de LípidoRESUMEN
Formation of peroxynitrite by the fast reaction between nitric oxide and superoxide anion may represent a critical control point in cells producing both species, leading to either down-regulation of the physiological effects of superoxide anion and nitric oxide by forming an inert product, nitrate, or to potentiation of their toxic effects by oxidation of nearby molecules by peroxynitrite. (The term peroxynitrite is used to refer to the sum of all possible forms of peroxynitrite anion and peroxynitrous acid unless otherwise specified.) In this report we demonstrate that, in spite of all the antioxidant defences present in human plasma, its interaction with peroxynitrite leads to generation of free radical intermediates such as (i) the ascorbyl radical, detected by direct EPR, (ii) the albumin-thiyl radical, detected by spin-trapping experiments with both N-tert-butyl-alpha-phenylnitrone and 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and (iii) a uric acid-derived free radical, detected as the DMPO radical adduct in plasma whose thiol groups were previously blocked with 5,5-dithiobis-(2-nitrobenzoic acid). The identity of the latter adduct was confirmed by parallel experiments demonstrating that it is not detectable in plasma pretreated with uricase, whereas it is formed in incubations of peroxynitrite with uric acid. Peroxynitrite-mediated oxidations were also followed by oxygen consumption and ascorbate and plasma-thiol depletion. Our results support the view that peroxynitrite-mediated one-electron oxidation of biomolecules may be an important event in its cytotoxic mechanism. In addition, the data have methodological implications by providing support for the use of EPR methodologies for monitoring both free radical reactions and ascorbate concentrations in biological fluids.