Effects of Cu, Zn and Cr salts on antioxidant enzyme activities In vitro of red blood cells of a marine fish Dicentrarchus labrax.

Effects of xenobiotics (potassium dichromate, copper sulphate and zinc chloride) in vitro on antioxidant enzyme activities and lipid peroxidation in sea bass erythrocytes were investigated. Total cell haemolysis was observed after 24 hr of exposure to 2 mm dichromate at 20 degrees C, 0.1 mm CuSO(4) and 1 mm ZnCl(2). 24 hr exposure to non-haemolytic concentrations of CuSO(4) and ZnCl(2) led to a concentration-related decrease in glutathione peroxidase activity. With dichromate, this activity was increased at the lowest concentrations (1-100 mum) and was decreased for the highest (0.5 and 1 mm). Dual effects were also found on dichromate-treated cells for manganese-dependent superoxide dismutase activity, whereas Zn(2+) had only inhibitory effects. Total superoxide dismutase activity was depressed by CuSO(4) and ZnCl(2); this effect was concentration dependent. With regard to catalase activity, ZnCl(2) and K(2)Cr(2)O(7) were found to be activators, whereas CuSO(4) was an inhibitor. Study of the effects of metals on lipid peroxidation was based on the release of TBA-reactive substances in the surrounding medium; 24 hr exposure to 1 mm dichromate, 10 mum CuSO(4) and, in particular, 100 mum ZnCl(2), increased the amount of this lipid peroxidation indicator. This work suggests that the defence system of sea bass red blood cells against active oxygen species can be compromised by metal ions, this imbalance being able to cause increased membrane lipid peroxidation. This study has demonstrated that seawater fish erythrocytes are a valid cell model for study of the effects in vitro of xenobiotics on antioxidant mechanisms.