RESUMO Introdução: O exercício físico intenso afeta o equilíbrio entre a produção de espécies reativas de oxigênio e a defesa antioxidante no músculo. A carnosina é um dipeptídeo citoplasmático composto pelos aminoácidos β-alanina e histidina. Objetivo: O presente trabalho teve como objetivo avaliar o efeito da carnosina e do seu precursor β-alanina nos danos oxidativos causados pelo exercício físico intenso no músculo sóleo de ratos. Métodos: Ratos Wistar machos pesando entre 200 e 240 g foram divididos em quatro grupos: controle, exercício, exercício + β-alanina e exercício + carnosina. Os animais dos grupos submetidos ao exercício correram em esteira por 60 minutos a 25 m/minuto. Fatores relacionados ao dano muscular e estresse oxidativo foram avaliados no soro sanguíneo e no homogenato do músculo sóleo. Resultados: O exercício promoveu lesão muscular conforme observado através do aumento da atividade sérica das enzimas aspartato aminotransferase e creatina quinase. Além disso, induziu o estresse oxidativo no músculo sóleo, observado pelo aumento da atividade das enzimas glutationa peroxidase e glutationa redutase, diminuição da concentração de glutationa reduzida e aumento na concentração de malondialdeído, um indicador de lipoperoxidação. A carnosina manteve os valores da atividade das enzimas creatina quinase, glutationa peroxidase e glutationa redutase, além da concentração de glutationa reduzida e malondialdeído próximos aos do grupo controle. Conclusão: Os resultados indicam que o tratamento prévio com carnosina protegeu o músculo sóleo de ratos contra os danos oxidativos e a consequente lesão provocada pelo exercício físico intenso. Nível de evidência II; Estudos terapêuticos-investigação dos resultados do tratamento.

ABSTRACT Introduction: Intense physical exercise affects the balance between the production of reactive oxygen species and antioxidant defense in the muscle. Carnosine is a cytoplasmic dipeptide composed of the amino acids β-alanine and histidine. Objective: This study aimed to evaluate the effect of carnosine and its precursor β-alanine on oxidative damage caused by intense physical exercise in the soleus muscle of rats. Methods: Male Wistar rats weighing between 200 and 240 g were divided into four groups: control, exercise, exercise + β-alanine and exercise + carnosine. The animals from the groups that underwent the exercise ran on a treadmill for 60 minutes at 25 m/minute. Factors related to muscle damage and oxidative stress were assessed in soleus muscle homogenate and blood serum. Results: The exercise promoted muscle damage, as observed through increased serum activity of enzymes aspartate aminotransferase and creatine kinase. It also induced oxidative stress in soleus muscle, as seen by the increased activity of the enzymes glutathione peroxidase and glutathione reductase, decreased concentration of reduced glutathione, and increased concentration of malondialdehyde, an indicator of lipid peroxidation. Carnosine kept the creatine kinase, glutathione peroxidase and glutathione reductase enzyme activity values, and the concentration of reduced glutathione and malondialdehyde, close to those of the control group. Conclusion: The results indicate that pretreatment with carnosine protected the rat soleus muscle against oxidative damage and consequent injury caused by intense physical exercise. Level of evidence II; Therapeutic studies-Investigating the treatment results.

RESUMEN Introducción: El ejercicio físico intenso afecta al equilibrio entre la producción de especies reactivas de oxígeno y la defensa antioxidante en el músculo. La carnosina es un dipéptido citoplasmático compuesto por los aminoácidos β-alanina e histidina. Objetivo: El presente trabajo tuvo como objetivo evaluar el efecto de la carnosina y de su precursor β-alanina en los daños oxidativos causados por el ejercicio físico intenso en el músculo sóleo de ratones. Métodos: Ratones Wistar machos pesando entre 200 y 240 g fueron divididos en cuatro grupos: control, ejercicio, ejercicio + β-alanina y ejercicio + carnosina. Los animales de los grupos sometidos al ejercicio corrieron en cinta durante 60 minutos a 25 m/minuto. Se evaluaron los factores relacionados al daño muscular y al estrés oxidativo en el suero sanguíneo y el homogenato del músculo sóleo. Resultados: El ejercicio promovió lesión muscular, conforme fuera observado a través del aumento de la actividad sérica de las enzimas aspartato aminotransferasa y creatina quinasa. Además, indujo al estrés oxidativo en el músculo sóleo, observado por el aumento de la actividad de las enzimas glutatión peroxidasa y glutatión reductasa, disminución de la concentración de glutatión reducido y aumento de la concentración de malondialdehído, un indicador de lipoperoxidación. La carnosina mantuvo los valores de actividad de las enzimas creatina quinasa, glutatión peroxidasa y glutatión reductasa, además de la concentración de glutatión reducido y malondialdehído cercanos a los del grupo de control. Conclusión: Los resultados indican que el tratamiento previo con carnosina protegió al músculo sóleo de ratones contra los daños oxidativos y la consiguiente lesión causada por el ejercicio físico intenso. Nivel de evidencia II; Estudios terapéuticos-Investigación de los resultados del tratamiento.

ABSTRACT The aim of this study was to characterize the mechanism of toxicity of fipronil on hepatocytes isolated from the rat and the effect of its biotransformation on the toxicological potential. The toxicity of fipronil was assessed by monitoring the oxygen consumption and mitochondrial membrane potential, intracellular ATP concentration, Ca2+ homeostasis and cell viability. The cell viability was evaluated by trypan blue exclusion in hepatocytes that were isolated from the normal rats and by the release of the enzymes alanine transaminase and aspartate transaminase in hepatocytes that were isolated from the normal rats or proadifen-pretreated rats. Fipronil reduced mitochondrial respiration in the cells that were energized with glutamate plus malate in a dose-dependent manner and dissipated the mitochondrial membrane potential that was accompanied by a reduction in ATP concentration and a disruption of intracellular Ca2+ homeostasis. The cell viability was affected by fipronil with higher potency in hepatocytes that were isolated from the normal rats, which indicated that the metabolism of this insecticide increased its toxicological potential. The results of this study indicated that the toxicity of fipronil to the hepatocytes was related to the inhibition of mitochondrial activity, which led to decreased ATP synthesis and a consequent alteration in intracellular Ca2+ homeostasis and ultimately resulted in cell death.

INTRODUÇÃO: os músculoesqueléticos são tecidos dinâmicos que podem alterar suas características fenotípicas proporcionando melhor adaptação funcional com estímulos variados. A L-tiroxina é um hormônio produzido pela glândula tireoide e tem sido utilizada como modelo experimental para estimulação de estresse oxidativo no músculo esquelético. A coenzima Q10 é uma provitamina lipossolúvel sintetizada endogenamente e naturalmente encontrada em alimentos como carne vermelha, peixes, cereais, brócolis e espinafre. Apresenta propriedade antioxidante e tem potencial no tratamento de doenças degenerativas e neuromusculares.OBJETIVO: avaliar o efeito protetor da coenzima Q10 no músculo sóleo de ratos frente aos danos oxidativos provocados pela L-tiroxina.MÉTODOS: os ratos foram distribuídos em quatro grupos de seis animais cada: Grupo 1 controle; Grupo 2 coenzima Q10; Grupo 3 L-tiroxina e Grupo 4 coenzima Q10 e L-tiroxina. Após a eutanásia, o sangue dos animais foi colhido e foi analisada a atividade sérica das enzimas creatina quinase CK e aspartato aminotransferase AST. No homogenato do músculo sóleo foram avaliados fatores relacionados ao estresse oxidativo.RESULTADOS: a coenzima Q10 protegeu o músculo sóleo dos danos provocados pela L-tiroxina e favoreceu a manutenção da atividade das enzimas antioxidantes glutationa redutase e glutationa peroxidase, da concentração de glutationa reduzida e oxidada, além de evitar a lipoperoxidação.CONCLUSÃO: os resultados indicam que a coenzima Q10 protege o músculo sóleo de ratos dos danos oxidativos provocados pela L-tiroxina.

INTRODUCTION: skeletal muscles are dynamic tissue that can change their phenotypic characteristics providing a better functional adaptation to different stimuli. L-thyroxine is a hormone produced by the thyroid gland and has been used as an experimental model for stimulation of oxidative stress in skeletal muscle. Coenzyme Q10 CoQ10 is a fat-soluble provitamin endogenously synthesized and found naturally in foods such red meat, fish, cereals, broccoli and spinach. It has antioxidant properties and potential in the treatment of degenerative and neuromuscular diseases.OBJECTIVE: to evaluate the protective effect of CoQ10 in the soleus muscle of rats against the oxidative damage caused by L-thyroxine.METHODS: the rats were divided in four groups of six animals each: Group 1 control; Group 2 coenzyme Q10; Group 3 L-thyroxine, and Group 4 coenzyme Q10 and L-thyroxine. After euthanasia, blood was collected and serum activity of the enzymes creatine kinase CK and aspartate aminotransferase AST was analyzed. In the soleus muscle homogenates the factors related to oxidative stress were assessed.RESULTS: CoQ10 protected the soleus muscle against the damage caused by L-thyroxine and favored the maintenance of the antioxidant enzymes glutathione reductase and glutathione peroxidase, the concentration of decreased and oxidized glutathione, and prevented lipid peroxidation.CONCLUSION: the results indicate that CoQ10 protects rat soleus muscle from oxidative damage caused by L-thyroxine.

INTRODUCCIÓN: los músculos esqueléticos son tejidos dinámicos que pueden alterar sus características fenotípicas proporcionando mejor adaptación funcional con estímulos variados. La L-tiroxina es una hormona producida por la glándula tiroides y ha sido utilizada como modelo experimental para estimulación de estrés oxidativo en el músculo esquelético. La coenzima Q10 es una provitamina liposoluble sintetizada endogénicamente y naturalmente encontrada en alimentos como carne roja, pescados, cereales, brócolis y espinaca. Presenta propiedad antioxidante y tiene potencial en el tratamiento de enfermedades degenerativas y neuromusculares.OBJETIVO: evaluar el efecto protector de la coenzima Q10 en el músculo soleo de ratas frente a los daños oxidativos provocados por la L-tiroxina.MÉTODOS: Las ratas fueron distribuidas en cuatro grupos de seis animales cada uno: Grupo 1 control; Grupo 2 coenzima Q10; Grupo 3 L-tiroxina y Grupo 4 coenzima Q10 y L-tiroxina. Después de la eutanasia, la sangre de los animales fue recogida y fue analizada la actividad sérica de las enzimas creatina quinasa CK y aspartato aminotransferasa AST. En el homogenato del músculo soleo fueron evaluados factores relacionados al estrés oxidativo.RESULTADOS: la coenzima Q10 protegió al músculo soleo de los daños provocados por la L-tiroxina y favoreció el mantenimiento de la actividad de las enzimas antioxidantes glutationa reductasa y glutationa peroxidasa, de la concentración de glutationa reducida y oxidada, además de evitar la lipoperoxidación.CONCLUSIÓN: los resultados indican que la coenzima Q10 protege al músculo soleo de ratas de los daños oxidativos provocados por la L-tiroxina

BACKGROUND: Gossypol is a chemical present in the seeds of cotton plants (Gossypium sp.) that reduces fertility in farm animals. Vitamin E is an antioxidant and may help to protect cells and tissues against the deleterious effects of free radicals. The aim of this study was to evaluate the mechanisms of reproductive toxicity of gossypol in rats and the protective effects of vitamin E. Forty Wistar rats were used, divided into four experimental groups (n = 10): DMSO/ saline + corn oil; DMSO/saline + vitamin E; gossypol + corn oil; and gossypol + vitamin E. RESULTS: Fertility was significantly reduced in male rats treated with gossypol in that a significant decrease in epididy-mal sperm count was observed (P < 0.05) and the number of offspring was significantly reduced in females mated with them (P < 0.05). This dysfunction was prevented by vitamin E. Gossypol caused a significant increase in the activity of the enzymes glutathione peroxidase (P < 0.01) and glutathione reductase (P < 0.01), but vitamin E did not reduce the enzyme activities (P > 0.05). The levels of reduced glutathione and pyridine nucleotides in testis homogen-ate were significantly reduced by gossypol (P < 0.05 and P < 0.01, respectively) and this reduction was accompanied by increased levels of oxidized glutathione (P < 0.05). Vitamin E showed a preventive effect on the changes in the levels of these substances. Gossypol significantly increased the levels of malondialdehyde (P < 0.01), a lipid peroxida-tion indicator, whereas treatment with vitamin E inhibited the action of the gossypol. Vitamin E prevented a decrease in mitochondrial ATP induced by gossypol (P < 0.05). CONCLUSIONS: This study suggests that the reproductive dysfunction caused by gossypol may be related to oxidative stress and mitochondrial bioenergetic damage and that treatment with vitamin E can prevent the infertility caused by the toxin.

BACKGROUND: The liver is an important organ for its ability to transform xenobiotics, making the liver tissue a prime target for toxic substances. The carotenoid bixin present in annatto is an antioxidant that can protect cells and tissues against the deleterious effects of free radicals. In this study, we evaluated the protective effect of bixin on liver damage induced by carbon tetrachloride (CCl4) in rats. RESULTS: The animals were divided into four groups with six rats in each group. CCl4 (0.125 mL kg-1 body wt.) was injected intraperitoneally, and bixin (5.0 mg kg-1 body wt.) was given by gavage 7 days before the CCl4 injection. Bixin prevented the liver damage caused by CCl4, as noted by the significant decrease in serum aminotransferases release. Bixin protected the liver against the oxidizing effects of CCl4 by preventing a decrease in glutathione reductase activity and the levels of reduced glutathione and NADPH. The peroxidation of membrane lipids and histopathological damage of the liver was significantly prevented by bixin treatment. CONCLUSION: Therefore, we can conclude that the protective effect of bixin against hepatotoxicity induced by CCl4 is related to the antioxidant activity of the compound.