Early Life Exposure to Ractopamine Causes Endocrine-Disrupting Effects in Japanese Medaka (Oryzias latipes)

摘要

beta-Agonists, which are used as human pharmaceuticals or feed additives, have been detected in aquatic environments. beta-Agonists have also been proposed for use in aquaculture. However, there are limited data available regarding the adverse effects of beta-agonists in aquatic organisms. In this study, ractopamine was selected as the representative beta-agonist, and medaka embryos were exposed at concentrations ranging from 5 to 625 mu g/L for 44 days. In contrast to what has been found in mammals, ractopamine caused no growth response in medaka. However, the transcriptional changes of genes related to the hypothalamic-pituitary-gonadal (HPG) axis, especially in females, suggested that beta-agonists may have the potential to disrupt the endocrine system. Moreover, genes involved in anti-oxidative activity or detoxification were affected in a gender-specific manner. These findings, particularly the effects on the endocrine system of fish, will advance our understanding of the ecotoxicity of beta-agonists.