Background: In this study, we investigated transcription and enzyme level responses of mussels Mytilus galloprovincialis exposed to hypoxic conditions. Genes for catalase (CAT), cytochrome P450, glutathione Stransferase (GST), metallothionein, superoxide dismutase (SOD), cytochrome c oxidase subunit 1 (COX-1), and NADH dehydrogenase subunit 2 were selected for study. Transcriptional changes were investigated in mussels exposed to hypoxia for 24 and 48 h and were compared to changes in control mussels maintained at normal oxygen levels. Activities of CAT, GST, and SOD enzymes, and lipid peroxidation (LPO) were also investigated in mussels following exposure to hypoxia for 24, 48, and 72 h. Results: Relative to the control group, the CAT activity decreased in all hypoxia treatments, while the activity of GST significantly increased in mussels exposed to hypoxia for 24 and 48 h, but decreased in those exposed for 72 h. The LPO levels were significantly higher in mussels in the 24-and 48-h hypoxia treatments than those in the control mussels, but there was no significant change in the SOD activities among all hypoxia treatments. Messenger RNA levels for the CAT, cytochrome P450, GST, metallothionein, and SOD genes were not significantly affected by hypoxic conditions for 48 h, but the expressions of the COX-1 and NADH dehydrogenase subunit 2 genes were significantly repressed in mussels in both the 24-and 48-h exposure treatments.

Benzo[k]fluoranthene (B[k]F) is one of numerous polycyclic aromatic hydrocarbons (PAHs) which is a persistent environmental contaminant in air and water.Upon B[k]F exposure, differential gene expression profiling was conducted in marine medaka fish (Oryzias javanicus) using subtractive hybridization. As a result, forty two differentially expressed candidate genes were induced in B[k]F-exposed fish as compared to control group, and the genes were associated with general metabolism, signal transduction, cell cycle, immune response, cytoskeleton, development, nucleotide/protein binding and some were non-categorized. These identified gene candidates have great potential to be developed as biomarkers for the identification of effects of B[k]F exposure in the environment. The results obtained in this study will offer insight to the physiological change induced by B[k]F exposure and will help assess the molecular mechanisms of B[k]F toxicity.