Histopathological, immunohistochemical, and endocrinological effects of cocaine in marine fish

Abstract

Residues of cocaine (COC) have been identified in different aquatic ecosystems. Once in the environment, COC could interact with non-target organisms. Several studies showed that environmentally concentrations of COC induced negative effects in invertebrate organism, especially freshwater, but there are still few studies on the effects of COC on marine vertebrates. The aim of this study is to investigate the histopathological, immunohistochemical, and endocrinological effects of COC in the European eels. The fish (30 adult specimens) will be acclimatized for one month and expose to nominal concentration of 200 ng.L-1 of COC (corresponding to the concentration found in Santos Bay, SP, Brazil, by Fontes et al. 2019). At the end of the experiment, all eels will be anesthetized and from each animal the gonads will be removed for the evaluation of morphology (histology), localization of enzymes involved in the steroidogenesis pathway (immunohistochemistry) and sex steroid levels as testosterone (DiaMetra), dihydrotestosterone (Abnova) and 17²-estradiol (DiaMetra) (endocrinological effects). The data obtained will provide an effective diagnosis of the environmental quality associated with COC, enabling the qualitative and quantitative identification of its impacts on marine ecosystems. (AU)