Evaluation of redox and bioenergetics states in the liver of vitamin A-treated rats.

Vitamin A is normally stored in the mammalian liver and is physiologically released depending on the need of the organism for the vitamin. However, there is a compelling evidence showing that even the liver is affected by conditions of high vitamin A intake. Based on these previously reported findings showing negative effects of vitamin A on mammalian tissues, we have investigated the effects of a supplementation with vitamin A at clinical doses (1000-9000 IU/kg day(-1)) on some rat liver parameters. We have analyzed hepatic redox environment, as well as the activity of the mitochondrial electron transfer chain in vitamin A-treated rats. Additionally, activity of the detoxifying enzyme glutathione S-transferase was checked. Also, caspase-3 and caspase-8 and tumor necrosis factor-alpha levels were quantified to assess either cell death or inflammation effects of vitamin A on rat liver. We found increased free radical production and, consequently, increased oxidative damage in biomolecules in the liver of vitamin A-treated rats. Interestingly, we found increased mitochondrial electron transfer chain activity, as well as glutathione-S-transferase enzyme activity. Neither caspases activity, nor tumor necrosis factor-alpha levels change in this experimental model. Our results suggest a pro-oxidant, but not pro-inflammatory effect of vitamin A on rat liver.