The toxic effects on the stress and immune responses in juvenile rockfish, Sebastes schlegelii exposed to hexavalent chromium

Juvenile Sebastes schlegelii (mean length 13.7 ± 1.7 cm, and mean weight 55.6 ± 4.8 g) were exposed for 4 weeks with the different levels of dietary chromium (Cr6+) concentration (0, 30, 60, 120 and 200 mg/L). The plasma cortisol and heat shock protein 70 was evaluated as stress indicators. Plasma cortisol was significantly increased in response to the dietary chromium exposure over 120 mg/kg at 2 and 4 weeks. Heat shock protein 70 was also notably increased over 120 mg/kg at 2 weeks and over 60 mg/kg at 4 weeks. In the immune response, immunoglobulin M was considerably increased in the concentration of 240 mg/kg at 2 weeks and over 120 mg/kg at 4 weeks. Lysozyme activity was considerably induced by the dietary hexavalent chromium exposure. A significant increase in plasma lysozyme activity was observed at 240 mg/kg after 2 weeks and over 60 mg/kg after 4 weeks, kidney lysozyme was also increased over 120 mg/kg at 2 and 4 weeks. The results demonstrate that dietary Cr exposure can induce a significant stress and immune stimulation.