Profiles of antioxidant gene expression and physiological changes by thermal and hypoosmotic stresses in black porgy (Acanthopagrus schlegeli)

We determined oxidative stress by measuring the expression and activity of 3 antioxidant enzymes [Cu/Zn-superoxide dismutase (Cu/Zn-SOD), catalase (CAT) and glutathione peroxidase (GPX)] in black porgy exposed to thermal (20 °C → 30 °C) and hypoosmotic (35 psu→10 psu and 0 psu) stresses. The expression and activity of antioxidant enzymes were significantly higher after exposure to 30 °C, 10 psu, and 0 psu. Furthermore, we measured H2O2 and lipid peroxidation (LPO) levels. As a result, H2O2 and LPO levels were significantly increased after exposure to thermal (20 °C → 30 °C) and hypoosmotic stress (35 psu→10 psu and 0 psu) stress. These results indicate that thermal and hypoosmotic stress induces oxidative stress in black porgy. Additionally, we investigated the changes due to thermal and hypoosmotic stress by measuring plasma cortisol and ion (Na+ and Cl−) levels. Plasma cortisol levels increased at 30 °C and at 10 psu and then decreased at 0 psu. However, plasma Na+ and Cl− levels did not change after exposure to thermal stress (30 °C), and decreased at 10 psu and 0 psu. In conclusion, thermal and hypoosmotic environments increase oxidative stress, thereby these results may be indicators of oxidative stress in black porgy.