RESUMO
PURPOSE: To investigate the effects of Murici extract on the brain excitability-dependent phenomenon known as cortical spreading depression (CSD) and on brain oxidative stress. METHODS: Adult and aged Wistar rats were supplemented with murici extract (150 mg/kg/day or 300 mg/kg/day) by gavage for fifteen days. Afterwards, the animals were submitted to a CSD electrophysiological recording and to brain oxidative stress evaluation. RESULTS: Our results showed that aging decreased CSD propagation velocity, catalase activity and glutathione/oxidized glutathione ratio (GSH/GSSG) in the brain cortex of the rats, and increased malondialdehyde (MDA) concentrations and superoxide dismutase (SOD) activity. The highest dose (300 mg/kg/day) of murici extract accelerated CSD, whereas the lowest (150mg/kg/day) decelerated, in both adult and aged animals. In contrast, aged animals supplemented with murici extract in both doses presented low MDA levels and high GSG/GSSG ratio in comparison to the control-aged animals. CONCLUSION: Murici extract supplementation seems to revert detrimental effects in aged brains and could be considered as a strategy in the treatment of pathologies related to aging and cortical spreading depression.
Assuntos
Envelhecimento/fisiologia , Antioxidantes/farmacologia , Córtex Cerebral/efeitos dos fármacos , Depressão Alastrante da Atividade Elétrica Cortical/efeitos dos fármacos , Malpighiaceae/química , Estresse Oxidativo/efeitos dos fármacos , Fatores Etários , Animais , Catalase/análise , Córtex Cerebral/metabolismo , Depressão Alastrante da Atividade Elétrica Cortical/fisiologia , Suplementos Nutricionais , Glutationa/análise , Dissulfeto de Glutationa/análise , Peroxidação de Lipídeos , Masculino , Malondialdeído/análise , Estresse Oxidativo/fisiologia , Ratos Wistar , Valores de Referência , Reprodutibilidade dos Testes , Superóxido Dismutase/análiseRESUMO
Abstract Purpose: To investigate the effects of Murici extract on the brain excitability-dependent phenomenon known as cortical spreading depression (CSD) and on brain oxidative stress. Methods: Adult and aged Wistar rats were supplemented with murici extract (150 mg/kg/day or 300 mg/kg/day) by gavage for fifteen days. Afterwards, the animals were submitted to a CSD electrophysiological recording and to brain oxidative stress evaluation. Results: Our results showed that aging decreased CSD propagation velocity, catalase activity and glutathione/oxidized glutathione ratio (GSH/GSSG) in the brain cortex of the rats, and increased malondialdehyde (MDA) concentrations and superoxide dismutase (SOD) activity. The highest dose (300 mg/kg/day) of murici extract accelerated CSD, whereas the lowest (150mg/kg/day) decelerated, in both adult and aged animals. In contrast, aged animals supplemented with murici extract in both doses presented low MDA levels and high GSG/GSSG ratio in comparison to the control-aged animals. Conclusion: Murici extract supplementation seems to revert detrimental effects in aged brains and could be considered as a strategy in the treatment of pathologies related to aging and cortical spreading depression.
Assuntos
Animais , Masculino , Envelhecimento/fisiologia , Córtex Cerebral/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Malpighiaceae/química , Antioxidantes/farmacologia , Valores de Referência , Depressão Alastrante da Atividade Elétrica Cortical/efeitos dos fármacos , Depressão Alastrante da Atividade Elétrica Cortical/fisiologia , Superóxido Dismutase/análise , Peroxidação de Lipídeos , Catalase/análise , Córtex Cerebral/metabolismo , Reprodutibilidade dos Testes , Fatores Etários , Ratos Wistar , Estresse Oxidativo/fisiologia , Dissulfeto de Glutationa/análise , Suplementos Nutricionais , Glutationa/análise , Malondialdeído/análiseRESUMO
BACKGROUND: Liver cirrhosis is associated with intestinal epithelial barrier dysfunction, which may be affected by oxidative stress. Studies in cirrhotic rats provided evidence for intestinal oxidative stress, but studies in cirrhotic patients are scarce. We have shown intestinal barrier dysfunction in patients with compensated cirrhosis. AIM: The present study aimed to investigate whether oxidative stress occurs in the intestinal mucosa of compensated cirrhotic patients and may contribute to barrier dysfunction. MATERIAL AND METHODS: Oxidative stress was studied in duodenal and sigmoid biopsies from 15 cirrhotic patients and 22 controls by analyzing transcription of genes involved in glutathione and uric acid metabolism using quantitative real-time polymerase chain reaction. Protein levels of glutathione and glutathione disulphide were measured and the glutathione/glutathione disulphide ratio was calculated as marker of oxidative stress. In addition, intestinal myeloperoxidase and fecal calprotectin were determined. RESULTS: Gene transcription of glutathione synthetase and glutathione reductase were significantly different in duodenal and sigmoid biopsies of cirrhotic patients vs. controls, but no alterations were found for other genes nor for glutathione, glutathione disulphide, glutathione/glutathione disulphide ratio and intestinal myeloperoxidase and fecal calprotectin concentrations. CONCLUSION: This study did not find indications for oxidative stress and low-grade inflammation in the small and large intestine of stable compensated cirrhotic patients. Although these preliminary findings need further validation, we found intestinal oxidative stress not to be a major mechanism contributing to epithelial barrier dysfunction in patients with compensated cirrhosis.
Assuntos
Colo Sigmoide/química , Duodeno/química , Mucosa Intestinal/química , Cirrose Hepática/metabolismo , Estresse Oxidativo , Adolescente , Adulto , Idoso , Biomarcadores/análise , Biópsia , Estudos de Casos e Controles , Fezes/química , Feminino , Regulação Enzimológica da Expressão Gênica/genética , Glutationa/análise , Dissulfeto de Glutationa/análise , Glutationa Redutase/genética , Glutationa Sintase/genética , Humanos , Complexo Antígeno L1 Leucocitário/análise , Cirrose Hepática/diagnóstico , Cirrose Hepática/genética , Masculino , Pessoa de Meia-Idade , Estresse Oxidativo/genética , Peroxidase/análise , Reação em Cadeia da Polimerase em Tempo Real , Transcrição Gênica , Adulto JovemRESUMO
Lung cancer is the most lethal cancer-related disease worldwide. Since survival rates remain poor, there is an urgent need for more effective therapies that could increase the overall survival of lung cancer patients. Lung tumors exhibit increased levels of oxidative markers with altered levels of antioxidant defenses, and previous studies demonstrated that the overexpression of the antioxidant enzyme catalase (CAT) might control tumor proliferation and aggressiveness. Herein, we evaluated the effect of CAT treatment on the sensitivity of A549 human lung adenocarcinoma cells toward various anticancer treatments, aiming to establish the best drug combination for further therapeutic management of this disease. Exponentially growing A549 cells were treated with CAT alone or in combination with chemotherapeutic drugs (cisplatin, 5-fluorouracil, paclitaxel, daunorubicin, and hydroxyurea). CalcuSyn(®) software was used to assess CAT/drug interactions (synergism or antagonism). Growth inhibition, NFκB activation status, and redox parameters were also evaluated in CAT-treated A549 cells. CAT treatment caused a cytostatic effect, decreased NFκB activation, and modulated the redox parameters evaluated. CAT treatment exhibited a synergistic effect among most of the anticancer drugs tested, which is significantly correlated with an increased H2O2 production. Moreover, CAT combination caused an antagonism in paclitaxel anticancer effect. These data suggest that combining CAT (or CAT analogs) with traditional chemotherapeutic drugs, especially cisplatin, is a promising therapeutic strategy for the treatment of lung cancer.
Assuntos
Adenocarcinoma/tratamento farmacológico , Antineoplásicos/farmacologia , Catalase/farmacologia , Neoplasias Pulmonares/tratamento farmacológico , Células A549 , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Sinergismo Farmacológico , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Dissulfeto de Glutationa/análise , Humanos , Peróxido de Hidrogênio/metabolismo , NF-kappa B/metabolismo , Proteínas de Neoplasias/metabolismo , Oxirredução , Compostos de Sulfidrila/análiseRESUMO
FUNDAMENTO: Estudos de intervenção mostraram aumento da mortalidade em pacientes que receberam betacaroteno. Contudo, não são conhecidos os mecanismos envolvidos nesse fenômeno. OBJETIVO: Avaliar a influência do betacaroteno sobre o estresse oxidativo e a expressão de conexina 43 em coração de ratos. MÉTODOS: Ratos Wistar, pesando aproximadamente 100 g, foram alocados em dois grupos: Grupo Controle (n = 30), que recebeu a dieta usada de rotina em nosso laboratório, e Grupo Betacaroteno (n = 28), que recebeu betacaroteno (na forma de cristal, adicionado e misturado à dieta) na dose de 500 mg de betacaroteno/kg de dieta. Os animais receberam tratamento até que atingissem entre 200 e 250 g, quando eram sacrificados. Foram coletados sangue, fígado e coração para realização de Western blotting e imunoistoquímica para conexina 43; foram realizados estudos morfométricos, dosagens de betacaroteno por cromatografia líquida de alta eficiência bem como de glutationa reduzida, glutationa oxidada e hidroperóxidos de lipídeos por análises bioquímicas. RESULTADOS: O betacaroteno foi detectado apenas no fígado dos animais do Grupo Betacaroteno (288 ± 94,7 µg/kg). Os níveis de glutationa reduzida/glutationa oxidada foram maiores no fígado e no coração dos animais do Grupo Betacaroteno (fígado - Grupo Controle: 42,60 ± 1,62; fígado - Grupo Betacaroteno: 57,40 ± 5,90; p = 0,04; coração: - Grupo Controle: 117,40 ± 1,01; coração - Grupo Betacaroteno: 121,81 ± 1,32 nmol/mg proteína; p = 0,03). O conteúdo de conexina 43 total foi maior no Grupo Betacaroteno. CONCLUSÃO: O betacaroteno apresentou efeito benéfico, caracterizado pelo aumento da comunicação intercelular e melhora do sistema de defesa antioxidante. Nesse modelo, os mecanismos não explicam a maior mortalidade observada com a suplementação de betacaroteno em estudos clínicos. (Arq Bras Cardiol. 2013; [online].ahead print, PP.0-0).
BACKGROUND: Intervention studies have shown an increased mortality in patients who received beta-carotene. However, the mechanisms involved in this phenomenon are still unknown. OBJECTIVE: Evaluate the influence of beta-carotene on oxidative stress and the expression of connexin 43 in rat hearts. METHODS: Wistar rats, weighing approximately 100 g, were allocated in two groups: Control Group (n=30), that received the diet routinely used in our laboratory, and Beta-Carotene Group (n = 28), which received beta-carotene (in crystal form, added and mixed to the diet) at a dose of 500 mg of beta-carotene/kg of diet. The animals received the treatment until they reached 200-250g, when they were sacrificed. Samples of blood, liver and heart were collected to perform Western blotting and immunohistochemistry for connexin 43; morphometric studies, dosages of beta-carotene by high-performance liquid chromatography as well as reduced glutathione, oxidized glutathione and lipids hydroperoxides were performed by biochemical analysis. RESULTS: Beta-carotene was detected only in the liver of Beta-Carotene Group animals (288 ± 94.7 µg/kg). Levels of reduced/oxidized glutathione were higher in the liver and heart of Beta-Carotene Group animals (liver - Control Group: 42.60 ± 1.62; liver - Beta-Carotene Group: 57.40 ± 5.90; p = 0.04; heart: - Control Group: 117.40 ± 1.01; heart - Beta-Carotene Group: 121.81 ± 1.32 nmol/mg protein; p = 0.03). The content of total connexin 43 was larger in Beta-Carotene Group. CONCLUSION: Beta-carotene demonstrated a positive effect, characterized by the increase of intercellular communication and improvement of anti-oxidizing defense system. In this model, mechanism does not explain the increased mortality rate observed with the beta-carotene supplementation in clinical studies. (Arq Bras Cardiol. 2013; [online].ahead print, PP.0-0).
Assuntos
Animais , Masculino , Ratos , /efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Vitaminas/farmacologia , beta Caroteno/farmacologia , Western Blotting , /metabolismo , Dissulfeto de Glutationa/análise , Ventrículos do Coração/química , Imuno-Histoquímica , Peróxidos Lipídicos/análise , Fígado/química , Ratos Wistar , Remodelação Ventricular , Vitaminas/efeitos adversos , Vitaminas/análise , beta Caroteno/efeitos adversos , beta Caroteno/análiseRESUMO
BACKGROUND: Intervention studies have shown an increased mortality in patients who received beta-carotene. However, the mechanisms involved in this phenomenon are still unknown. OBJECTIVE: Evaluate the influence of beta-carotene on oxidative stress and the expression of connexin 43 in rat hearts. METHODS: Wistar rats, weighing approximately 100 g, were allocated in two groups: CONTROL GROUP (n=30), that received the diet routinely used in our laboratory, and Beta-Carotene Group (n = 28), which received beta-carotene (in crystal form, added and mixed to the diet) at a dose of 500 mg of beta-carotene/kg of diet. The animals received the treatment until they reached 200-250 g, when they were sacrificed. Samples of blood, liver and heart were collected to perform Western blotting and immunohistochemistry for connexin 43; morphometric studies, dosages of beta-carotene by high-performance liquid chromatography as well as reduced glutathione, oxidized glutathione and lipids hydroperoxides were performed by biochemical analysis. RESULTS: Beta-carotene was detected only in the liver of Beta-Carotene Group animals (288 ± 94.7 µg/kg). Levels of reduced/oxidized glutathione were higher in the liver and heart of Beta-Carotene Group animals (liver - CONTROL GROUP: 42.60 ± 1.62; liver - Beta-Carotene Group: 57.40 ± 5.90; p = 0.04; heart: - CONTROL GROUP: 117.40 ± 1.01; heart - Beta-Carotene Group: 121.81 ± 1.32 nmol/mg protein; p = 0.03). The content of total connexin 43 was larger in Beta-Carotene Group. CONCLUSION: Beta-carotene demonstrated a positive effect, characterized by the increase of intercellular communication and improvement of anti-oxidizing defense system. In this model, mechanism does not explain the increased mortality rate observed with the beta-carotene supplementation in clinical studies.
Assuntos
Conexina 43/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Vitaminas/farmacologia , beta Caroteno/farmacologia , Animais , Western Blotting , Conexina 43/metabolismo , Dissulfeto de Glutationa/análise , Ventrículos do Coração/química , Imuno-Histoquímica , Peróxidos Lipídicos/análise , Fígado/química , Masculino , Ratos , Ratos Wistar , Remodelação Ventricular , Vitaminas/efeitos adversos , Vitaminas/análise , beta Caroteno/efeitos adversos , beta Caroteno/análiseRESUMO
Ischaemia reperfusion injury is a pathophysiological event that occurs after cardiac surgery with extracorporeal circulation. This clinical event has been associated with the induction of oxidative and inflammatory damage in atrial tissue. Here, we tested whether combined omega 3 polyunsaturated fatty acids (n-3 PUFA)-antioxidant vitamin protocol therapy reduces oxidative and inflammatory cardiac tissue damage. This trial assigned 95 either-sex patients to supplementation with n-3 PUFA (2 g/day), or matching placebo groups, 7 days before on-pump surgery. Antioxidant vitamins C (1 g/day) and E (400 IU/day) or placebo were added from 2 days before surgery until discharge. Blood and atrial tissue samples were obtained during the intervention. Reduced/oxidized glutathione (GSH/GSSG) ratio, malondialdehyde (MDA) and protein carbonylation were determined in atrial tissue. Leucocyte count and high-sensitivity C-reactive protein (hs-CRP) in blood plus nuclear factor (NF)-κappaB activation in atrial tissue served for inflammation assessment. Lipid peroxidation and protein carbonylation were 27.5 and 24% lower in supplemented patients (p < 0.01). GSH/GSSG ratio was 38.1% higher in supplemented patients compared with placebo (p < 0.01). Leucocyte count and serum hs-CRP levels were markedly lower throughout the protocol in supplemented patients (p < 0.01). Atrial tissue NF-κB DNA activation in supplemented patients was 22.5% lower than that in placebo patients (p < 0.05). The combined n-3 PUFA-antioxidant vitamin protocol therapy here proposed reduced the oxidative stress and inflammation biomarkers, in patients undergoing on-pump cardiac surgery.
Assuntos
Antioxidantes/administração & dosagem , Suplementos Nutricionais , Circulação Extracorpórea/métodos , Inflamação/tratamento farmacológico , Estresse Oxidativo , Procedimentos Cirúrgicos Torácicos/métodos , Idoso , Análise de Variância , Ácido Ascórbico/administração & dosagem , Proteína C-Reativa/análise , Método Duplo-Cego , Quimioterapia Combinada , Ácidos Graxos Ômega-3/administração & dosagem , Feminino , Dissulfeto de Glutationa/análise , Humanos , Peroxidação de Lipídeos , Modelos Logísticos , Masculino , Malondialdeído/análise , Pessoa de Meia-Idade , NF-kappa B/metabolismo , Carbonilação Proteica , Vitamina E/administração & dosagemRESUMO
Apocynin has been widely used as an NADPH oxidase inhibitor in many experimental models. However, concern regarding the efficacy, selectivity, and oxidative side effects of the inhibitor is increasing. In this study, our aim was to characterize the pro-oxidant properties of apocynin and the structurally-related compounds vanillin and vanillic acid. Glutathione (GSH), cysteine, ovalbumin, and the coenzyme NADPH were chosen as potential target biomolecules that could be affected by transient free radicals from apocynin, vanillin and vanillic acid. Additionally, trolox and rifampicin were used as models of hydroquinone moieties, which are particularly susceptible to oxidation. Transient radicals were generated by horseradish peroxidase/hydrogen peroxide-mediated oxidation. In the presence of apocynin, oxidation of GSH was increased seven-fold, and the product of this reaction was identified as GSSG. Similar results were obtained for oxidation of cysteine and ovalbumin. Oxidation of the coenzyme NADPH increased more than 100-fold in the presence of apocynin. Apocynin also caused rapid oxidation of trolox and rifampicin to their quinone derivatives. In conclusion, the pro-oxidant activity of apocynin is related to its previous oxidation leading to transient free radicals. This characteristic may underlie some of the recent findings regarding beneficial or deleterious effects of the phytochemical.
Assuntos
Acetofenonas/farmacologia , Inibidores Enzimáticos/farmacologia , Oxirredução/efeitos dos fármacos , Espécies Reativas de Oxigênio/farmacologia , Acetofenonas/metabolismo , Benzaldeídos/metabolismo , Benzaldeídos/farmacologia , Cisteína/metabolismo , Inibidores Enzimáticos/metabolismo , Radicais Livres/metabolismo , Radicais Livres/farmacologia , Glutationa/metabolismo , Dissulfeto de Glutationa/análise , Dissulfeto de Glutationa/biossíntese , Ovalbumina/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Ácido Vanílico/metabolismo , Ácido Vanílico/farmacologiaRESUMO
INTRODUCTION: Glutathione and glutathione disulfide can be determined by capillary zone electrophoresis; however, the frequent use of acidic precipitation of protein from samples prior to analysis generates an acidic matrix of strength and pH that may cause changes in the method sensitivity, comigration of species or changes in the equilibria that relate both species in cells or fluids. OBJECTIVE: To optimise electrophoretic conditions for glutathione and glutathione disulfide determination, and to improve pre-analytical treatment for better visualization of the signals of both peptides in an acidic matrix. METHODOLOGY: The method consisted of direct photometric detection at 185 nm and 300 mm borate at pH 7.6 as background electrolyte. The variables under study were voltage applied, injection time, capillary length and electrolyte pH. Seedlings were hydroponically grown and the peptides were extracted with metaphosphoric acid. RESULTS: The resulting acidic matrix was previously treated with the same background electrolyte to prevent comigration and to improve signal resolution. The optimised method showed good reproducibility and linearity, with correlation coefficients above 0.999 and detection limits below 3 microM, and determination of both analytes in less than 3 min. Analyte recovery in the process was in the 88-104% range. The concentration range found in hydroponically grown tomato plants, irrespective of copper level, was 45-100 nmol/g fresh weight for glutathione and below 56 nmol/g fresh weight for glutathione disulfide. CONCLUSION: The results obtained here support the applicability of the method to the fast and simultaneous determination of glutathione and glutathione disulfide in tissue of shoots and roots of plants grown under either normal or stressful conditions.
Assuntos
Cobre/toxicidade , Eletroforese Capilar/métodos , Dissulfeto de Glutationa/análise , Glutationa/análise , Raízes de Plantas/efeitos dos fármacos , Brotos de Planta/efeitos dos fármacos , Raízes de Plantas/química , Brotos de Planta/química , Padrões de Referência , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Rhabdomyolysis-induced oxidative stress is associated with morphological and functional damage to the kidney and other organs, but applications of this model in the lung are still lacking. The aim of the present study was to determine the relationship between oxidative stress and the morphological changes occurring in the lungs of rats subjected to rhabdomyolysis. Rhabdomyolysis was induced by intramuscular glycerol injection (50% v/v, 10 ml/kg), and the control group was injected with saline vehicle. Arterial blood samples were drawn at 0, 2, 4, and 6 hrs for measurement of arterial gases, creatine kinase activity, and plasma free F2-isoprostane levels. Six hours later, the lungs were removed to determine the wet-to-dry weight ratio, reduced glutathione (GSH) and GSH disulfide (GSSG) levels, and activity of antioxidant enzymes (catalase [CAT], superoxide dismutase [SOD], and GSH peroxidase [GSH-Px]). Protein carbonylation and lipid peroxidation were assessed in the lungs by measurement of carbonyl and malondialdehyde (MDA) production, respectively. Bronchoalveolar lavage, cell counts, and lung ultrastructural studies were also performed. Six hours after glycerol injection, arterial PO2 and PCO2 were 23% and 38% lower, respectively, and plasma free F2-isoprostane levels were 72% higher, compared with control values. In lungs, protein carbonyl and MDA production were 58% and 12% higher, respectively; the GSH:GSSG ratio and GSH-Px activity were 43% and 60% lower, respectively; and activities of CAT and SOD showed no significant differences compared with controls. Rhabdomyolysis-induced ultrastructural impairment of the lung showed Type II cell damage, extracytoplasmic lamellar bodies and lack of tubular myelin reorganization, endothelial cellular edema, and no disruption of the alveolar-capillary barrier. These results provide evidence that rhabdomyolysis could induce tissue injury associated with increased oxidative stress, suggesting the contribution of oxidative stress to the pathogenic mechanism of acute lung injury.
Assuntos
Pneumopatias/etiologia , Pneumopatias/metabolismo , Pulmão/ultraestrutura , Estresse Oxidativo/fisiologia , Rabdomiólise/complicações , Animais , Líquido da Lavagem Broncoalveolar/química , Líquido da Lavagem Broncoalveolar/citologia , Dióxido de Carbono/sangue , Catalase/análise , Catalase/metabolismo , F2-Isoprostanos/sangue , Glutationa/análise , Glutationa/metabolismo , Dissulfeto de Glutationa/análise , Dissulfeto de Glutationa/efeitos dos fármacos , Glutationa Peroxidase/análise , Glutationa Peroxidase/metabolismo , Glicerol/toxicidade , Peroxidação de Lipídeos/efeitos dos fármacos , Peroxidação de Lipídeos/fisiologia , Pulmão/química , Pulmão/metabolismo , Pneumopatias/patologia , Masculino , Microscopia Eletrônica de Transmissão , Oxigênio/sangue , Carbonilação Proteica/efeitos dos fármacos , Carbonilação Proteica/fisiologia , Ratos , Ratos Wistar , Testes de Função Respiratória , Rabdomiólise/induzido quimicamente , Superóxido Dismutase/análise , Superóxido Dismutase/metabolismoRESUMO
We investigated the hypothesis that thallium (Tl) interactions with the glutathione-dependent antioxidant defence system could contribute to the oxidative stress associated with Tl toxicity. Working in vitro with reduced glutathione (GSH), glutathione reductase (GR) or glutathione peroxidase (GPx) in solution, we studied the effects of Tl+ and Tl3+ (1-25 microM) on: (a) the amount of free GSH, investigating whether the metal binds to GSH and/or oxidizes it; (b) the activity of the enzyme GR, that catalyzes GSH regeneration; and (c) the enzyme GPx, that reduces hydroperoxide at expense of GSH oxidation. We found that, while Tl+ had no effect on GSH concentration, Tl3+ oxidized it. Both cations inhibited the reduction of GSSG by GR and the diaphorase activity of this enzyme. In addition, Tl3+ per se oxidized NADPH, the cofactor of GR. The effects of Tl on GPx activity depended on the metal charge: Tl+ inhibited GPx when cumene hydroperoxide (CuOOH) was the substrate, while Tl(3+)-mediated GPx inhibition occurred with both substrates. The present results show that Tl interacts with all the components of GSH/GSSG antioxidant defence system. Alterations of this protective pathway could be partially responsible for the oxidative stress associated with Tl toxicity.