Environmental acidification triggers oxidative stress and enhances globin expression in zebrafish gills

Animals in many aquatic ecosystems must cope with changing environmental parameters, such as temperature, oxygen availability or pH. We have investigated the molecular responses to acidification in the gills and body of zebrafish (Danio rerio) by means of quantitative real-time PCR. Expression levels of typical stress genes and genes for antioxidant defense were strongly enhanced in gills, and to lesser extents in the body, suggesting that acidification leads to oxidative stress. Surprisingly, the globins were found to be among the most prominent stress–responsive proteins in our study. Myoglobin showed the strongest response of all investigated genes in the gills, as confirmed by Western blotting. These findings agree with the role of globins in oxidative energy metabolism, but may also hint at a specific function in antioxidative defense.