Effect of hypoosmotic and thermal stress on gene expression and the activity of antioxidant enzymes in the cinnamon clownfish, Amphiprion melanopus

We studied oxidative stress in cinnamon clownfish exposed to hypoosmotic (35 psu → 17.5 psu and 17.5 psu with prolactin (PRL)) and low temperature (28°C → 24°C and 20°C) conditions by measuring the expression and activity of Cu/Zn-superoxide dismutase (Cu/Zn-SOD), catalase (CAT), and glutathione peroxidase (GPX). The expression and activity of the antioxidant enzymes were significantly higher after the fish were exposed to 24°C, 20°C, and 17.5 psu, and expression was repressed by PRL treatment. Furthermore, we measured H2O2 and lipid peroxidation levels and found that they were significantly higher after exposure to the hypoosmotic and low-temperature environments. Additionally, we investigated changes in plasma AST and ALT levels after exposure to low temperature and hypoosmotic stress. These levels increased upon exposure of the clownfish to 24°C, 20°C, and 17.5 psu, but the levels of these parameters decreased in the 17.5 psu with PRL treatment during a salinity change. The results indicate that hypoos...