Bile And Liver Metallothionein Behavior In Copper-exposed Fish.

The present study analyzed metallothionein (MT) excretion from liver to bile in Nile Tilapia (Oreochromis niloticus) exposed to sub-lethal copper concentrations (2mgL(-1)) in a laboratory setting. MTs in liver and bile were quantified by spectrophotometry after thermal incubation and MT metal-binding profiles were characterized by size exclusion high performance liquid chromatography coupled to ICP-MS (SEC-HPLC-ICP-MS). Results show that liver MT is present in approximately 250-fold higher concentrations than bile MT in non-exposed fish. Differences between the MT profiles from the control and exposed group were observed for both matrices, indicating differential metal-binding behavior when comparing liver and bile MT. This is novel data regarding intra-organ MT comparisons, since differences between organs are usually present only with regard to quantification, not metal-binding behavior. Bile MT showed statistically significant differences between the control and exposed group, while the same did not occur with liver MT. This indicates that MTs synthesized in the liver accumulate more slowly than MTs excreted from liver to bile, since the same fish presented significantly higher MT levels in liver when compared to bile. We postulate that bile, although excreted in the intestine and partially reabsorbed by the same returning to the liver, may also release MT-bound metals more rapidly and efficiently, which may indicate an efficient detoxification route. Thus, we propose that the analysis of bile MTs to observe recent metal exposure may be more adequate than the analysis of liver MTs, since organism responses to metals are more quickly observed in bile, although further studies are necessary.

SEMELHANÇAS ENTRE UPTAKE E TRACE: CONSIDERAÇÕES SOBRE TRADUÇÃO

This study is a reflection about the similarities between uptake and trace, and translation taken as an event - at once possible and impossible - which deflagrates and constitutes meaning through the language game played by the subjects of communication: text-translator. Both Austin and Derrida, each one on his own way, show that meaning is part of the human language process. The uptake, in Austin s point of view, guarantees the existence of human language, assured by a process of recognition between the subjects of communication, process through which the production of meaning takes place. The trace, according to Derrida, deflagrates, through the human language, the crashing of meaning and destroys the possibility of someone reaching the origin. In this study, taking into consideration the similarities between uptake and trace, I try to disclose translation taken as an event which at once contaminates the languages and is contaminated by them.