RESUMEN
Twenty-seven rats were divided into three groups and fed on diets containing 0.3, 6 or 60 RE (retinol equivalent) retinyl palmitate/g food. After 7 weeks, hepatic vitamin A uptake was found to be more efficient in vitamin A-deficient rats than in rats given adequate vitamin A. We showed that during the metabolic adaptation of the animals to the level of vitamin A in the diet, extensive modifications occur in the antioxidant defences of the organism. In parallel with the increase in the level of vitamin A, the decrease in the level of alpha-tocopherol in the plasma can bring about a greater susceptibility of the lipoproteins to oxidative stress. Similarly, the decrease in the hepatic alpha-tocopherol level and in glutathione peroxidase activity leads to the weakening of the liver's antioxidant defences.
Asunto(s)
Antioxidantes/metabolismo , Hígado/metabolismo , Estado Nutricional , Vitamina A/administración & dosificación , Vitamina A/sangre , Animales , Dieta , Diterpenos , Glutatión Peroxidasa/metabolismo , Masculino , Ratas , Ratas Sprague-Dawley , Ésteres de Retinilo , Vitamina A/análogos & derivados , Vitamina A/metabolismo , Vitamina E/sangre , Vitamina E/metabolismoAsunto(s)
Pan/análisis , Manipulación de Alimentos , Micotoxinas , Ocratoxinas/análisis , Calor , Ocratoxinas/químicaRESUMEN
The effects of catechin, a well-known in vitro antioxidant, on 3T3 Swiss fibroblasts are studied under different conditions of oxidative stress leading to cell proliferation or cytotoxicity. Various levels of reactive oxygen species (ROS), generated extracellularly by the xanthine-xanthine oxidase (X-XO) system, are at the origin of the biphasic effect on DNA synthesis by 3T3 Swiss fibroblasts. The addition of 10(-2) U XO/mL, in the absence of exogenous X, catalyzes the production of low levels of O2-. and H2O2 in the extracellular medium, which stimulate DNA synthesis and cell division. The increase in the level of ROS, by addition of increasing X concentrations, did not enhance this effect proportionally. On the contrary, high levels of ROS inhibit DNA synthesis, the cytotoxicity induced being proportional to the level of H2O2 generated by the enzyme system. Catechin does not significantly modify DNA synthesis induced by low levels of ROS, but protects in a dose-dependent manner against the cytoxicity of high levels of ROS.
Asunto(s)
Antioxidantes/farmacología , Catequina/farmacología , Peróxido de Hidrógeno/metabolismo , Superóxidos/metabolismo , Células 3T3 , Alopurinol/farmacología , Animales , Catalasa/farmacología , División Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , ADN/biosíntesis , ADN/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Cinética , Ratones , Estrés Oxidativo , Especies Reactivas de Oxígeno/farmacología , Análisis de Regresión , Superóxido Dismutasa/farmacología , Timidina/metabolismo , Xantina , Xantina Oxidasa/farmacología , Xantinas/farmacologíaRESUMEN
Descriptions of the effects of paraquat (P2+) on the peroxidation of liver microsomes are very divergent. Therefore, the presence of ferric iron in the medium and the activity of microsomal mixed-function oxidase system are two factors that we have taken into consideration to explain the discrepancies. The results showed that 100 microM P2+ potentializes the slight production of MDA induced by low concentrations of Fe3+ (< or = 15 microM). In these conditions, P+., arising from the one-step reduction of P2+ by NADPH-cytochrome C reductase, could reduce Fe3+ and cause the formation of species that initiate peroxidation. However, unlike the results obtained with CBrCl3, for animals induced by phenobarbital (Ph), the production of MDA in the presence of FeCl3 and of P2+ was weaker than for the controls. The establishment of a new Fe3+/Fe2+ equilibrium owing to increased production of P+. could be responsible.
Asunto(s)
Hierro/farmacología , Peroxidación de Lípido/efectos de los fármacos , Microsomas Hepáticos/metabolismo , Oxigenasas de Función Mixta/biosíntesis , Paraquat/farmacología , Fenobarbital/farmacología , Animales , Sistema Enzimático del Citocromo P-450/metabolismo , Membranas Intracelulares/efectos de los fármacos , Membranas Intracelulares/metabolismo , Cinética , Masculino , Malondialdehído/metabolismo , Lípidos de la Membrana/metabolismo , Microsomas Hepáticos/efectos de los fármacos , NADPH-Ferrihemoproteína Reductasa/metabolismo , Ratas , Ratas Sprague-DawleyRESUMEN
Direct membrane injury by CCl4, in situations excluding metabolic activation, was evaluated in saponin-permeabilized hepatocytes and in microsomes by measuring immediate Ca2+ efflux. A good correlation appears between the Ca2+ efflux and the level of CCl4 in the membrane and also the variations in fluidity. Mixtures of CCl4 with water-soluble vehicles were used to improve the dispersion of CCl4 in the medium. The mixtures varied in their ability to elicit the membrane effects of CCl4. The performance of ethanol and, to a lesser degree, other alcohols, suggests the existence of a water stable structural organization between CCl4 and these amphiphilic vehicles, facilitating the transfer of CCl4 to the membrane.