Oxidative stress and gene expression in diverse tissues of Oryzias javanicus exposed to 17β-estradiol

Transcriptional changes in the expression of stress-related genes (catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase, metallothionein, and ubiquitin) in intestinal, liver and muscle tissues of Javanese medaka (Oryzias javanicus) exposed to 17-estradiol (E2) were investigated using real-time quantitative PCR. The lipid peroxidation levels and superoxide dismutase activity in liver tissues was also examined at various exposure concentrations. In fish exposed to 10, 100 and 1000 g/L E2 the level of catalase mRNA increased significantly in intestinal and muscle tissues, while expression of the glutathione peroxidase gene showed the opposite trend in liver and muscle tissues. Expression of the glutathione S-transferase gene increased in a dose-dependent manner in liver and muscle tissues of fish exposed to E2, relative to the non-exposed control group. The level of glutathione reductase mRNA increased markedly in the liver tissues of all fish exposed to 100 and 1000 g/L E2, but decreased in intestinal tissues. The metallothionein gene was strongly downregulated in intestinal and liver tissues of fish exposed to E2, but slightly upregulated in muscle tissues. In all fish exposed to 100 and 1000 g/L E2 expression of the ubiquitin gene increased markedly in liver and muscle tissue, but not in intestinal tissues. Lipid peroxidation and superoxide dismutase activities increased significantly in all 17-estradiol treatment groups, and were correlated to the exposure concentration. Thus, E2 exposure differentially affected the transcription of a range of stress-related genes in various tissues of Javanese medaka, suggesting that analysis of transcriptional changes in these genes could be used as a rapid assay of the effects of E2 exposure.