Background

Biliary excretion is an alternative way to analyze several chemical pollutants in aquatic organisms. Fish bile has been routinely applied as a biomarker for environmental contamination for several decades, although the focus until recently has been only the detection of environmental contaminants, and not the evaluation of possible biochemical effects, such as differential protein expression. However, the fish bile proteome has been recently validated as a tool for monitoring the impact of environmental contaminants on fish metabolism. These include the possible deleterious effects of polycyclic aromatic hydrocarbons (Pampanin et al., 2014), metals and metalloids (Hauser-Davis et al., 2012a) and complex mixtures (Hauser-Davis et al., 2012b), among other pollutants. However, this is a very recent field, and studies are still lacking in this regard. In this context, fish bile contains high amounts of lipids and bile salts, which interfere in protein quantification, 1D- and 2D-electrophoresis and mass spectrometry analyses (Hauser-Davis et al., 2012b). Thus, clean-up procedures are of the utmost importance in order to obtain reproducible results and adequately prepare this fluid for subsequent proteomic applications.