Metabolic changes in marine medaka fish (Oryzias javanicus) in response to acute 4-nonlyphenol toxicity

The differentially expressed genes in the liver tissue of the marine medaka fish, Oryzias javanicus , were profiled using an oligo-microarray (EnviHaz Fish Array ver. 01) after the fish were exposed to 20 µg/L 4-nonylphenol (4-NP) for 12, 24, 48, or 72 h to determine the metabolic and physiological changes with exposure time. The transcriptomic changes were highly dynamic in the 4-NP-exposed fish in that among the 216 differentially expressed genes identified in all four exposed fish groups, 106 genes (49.1%) appeared after a specific exposure time. The differentially expressed genes were used to predict the changes that occurred in the metabolic pathways and processes in response to 4-NP exposure. Many physiological and metabolic changes were detected in the early phase of exposure. Significant vitellogenin expression and an estrogenic stimulus response were observed in the fish exposed to 4-NP for 48 h. These results extend our understanding of the biological responses to environmental chemicals at the molecular level and will allow the toxic effects of environmental chemicals, especially endocrine-disrupting chemicals, to be evaluated.