Tools to assess effects of human pharmaceuticals in fish: A case study with gemfibrozil

There is an increasing need to assess animal welfare and subtle alterations that may indicate the presence of environmental stressors. Among the most widely used endpoints are the assessment of the activities of specific enzymes and the alterations of the expression levels of target genes. Enzymes associated with oxidative stress are frequently assessed but the results frequently render enzyme-dependent altered levels that make analyses difficult. In this study, Sparus aurata (gilthead sea bream) juveniles, were exposed, via water, to gemfibrozil (GEM) for a 96 h period to i) validate methods to measure total oxidative status (TOS), total antioxidant capacity (TAC), and esterase activity (EA) in gills; ii) study the relation between assessed gills' oxidative stress responses and the mRNA levels of genes related to stress and immune function (in the gills and head kidney); iii) contribute to the knowledge of the effects of this human pharmaceutical on marine fish species. Overall, the obtained data confirmed the methodological precision and accuracy of TOS, TAC and EA measurements in the gills. GEM exposure did not alter TAC in gills but increased TOS. GEM modulated mRNA levels of genes, such as glutathione peroxidase 1 (gpx1) and interleukin 1 beta (il1 beta) in the gills and head kidney of S. aurata.