, Volume 60, Issue 1, pp 1-6

The influence of fasting on liver sulfhydryl groups, glutathione peroxidase and glutathione-S-transferase activities in the rat

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Abstract

Sulfhydryl groups, glutathione peroxidase (GPx) and glutathione-S-transferase (GST) are important elements of the antioxidant defence in the organism. The efficacy of their antioxidant action is influenced by many factors. In this work, the effect of fasting on total, protein-bound and nonprotein sulfhydryl groups and on the activity of liver and serum GPx and GST in rats were determined. Male Wistar rats were divided into two groups: non-fasted and 18-hour fasted. In fasted animals liver content of nonprotein sulfhydryl groups (represented predominantly by reduced glutathione; GSH) was diminished by 22% in comparison to non-fasted group, whereas total and protein-bound-SH groups were unaffected. The activity of liver and serum GPx was unchanged in food deprived rats. In these animals the activity of GST in serum was reduced by 26%. Fasting had no significant effect on the activity of GST in the liver. Our results demonstrate that in rats deprived of food for 18 hours liver and serum GPx and GST are not involved in protection against action of reactive oxygen species formed during fasting. The observed drop in the content of liver nonprotein sulfhydryl groups without concomitant rise in the activity of GPx and GST indicates that this effect may be due to augmented degradation of GSH, its potentiated efflux from hepatocytes and formation of conjugates with intermediates arising as a result of reactive oxygen species action.

Resumen

Los grupos sulfhidrilo, la actividad glutation peroxidasa (GPx) y glutation-S-transferasa son importantes en la actividad antioxidante del organismo, cuya eficacia depende de diversos factores. En el presente trabajo, se determina la influencia del ayuno sobre el contenido hepático de grupos sulfhidrilo totales, unidos a proteínas y no protéicos en rata, así como sobre la actividad glutation peroxidasa y glutation-S-transferasa en suero e hígado. Ejemplares macho de Wistar se dividieron en dos grupos, uno control y otro sometido a ayuno de 18 horas. En este último, el contenido hepático de grupos-SH no proteico (esencialmente, glutatión reducido, GSH) disminuyó un 22% en comparación con el grupo control, sin cambios significativos en el contenido de grupos-SH totales y unidos a proteínas. La actividad de glutation peroxidasa en suero e hígado no se modifica por el ayuno, mientras que desciende la actividad glutation-S-transferasa sérica en un 26%. Tampoco varía significativamente la actividad glutation-S-transferasa en hígado. Los resultados obtenidos indican que la glutation peroxidasa y glutation-S-transferasa no están implicadas en la protección contra la acción de las especies reactivas de oxígeno formadas durante el ayuno. La caída del contenido hepático de grupos sulfhidrilo no proteicos sin aumento simultáneo de la actividad glutation peroxidasa y glutation-S-transferasa indica que el efecto puede deberse a degradación aumentada de GSH, su flujo incrementado desde los hepatocitos y formación de conjugados, como resultado de su actividad antioxidante.