The immune responses in juvenile rockfish,Sebastes schlegelii for the stress by the exposure to the dietary lead (II)

The aim of this study was to evaluate the lead toxic effects on the stress parameters and immune responses of Sebastes schlegelii. Juvenile rockfish, S. schlegelii (mean length 14.2 ± 1.9 cm, and mean weight 57.3 ± 5.2 g) were exposed for 4 weeks with the different levels of dietary lead (Pb²⁺) at 0, 30, 60, 120 and 240 mg/L. The plasma cortisol and heat shock protein 70 was evaluated as stress indicators. The plasma cortisol of S. schlegelii was significantly increased in response to the dietary lead exposure over 60 mg/kg at 2 weeks. After 4 weeks, the significant increase in the plasma cortisol was observed at 30 and 60 mg/kg, but the level was decreased over 120 mg/kg. The heat shock protein 70 of S. schlegelii was also notably elevated over 60 mg/kg for 4 weeks. In the immune response, the immunoglobulin M of S. schlegelii was considerably increased over 120 mg/kg for 4 weeks. A significant increase was observed in lysozyme activity. The plasma lysozyme activity of S. schlegelii was elevated over 120 mg/kg after 2 weeks and 60 mg/kg after 4 weeks, and kidney lysozyme activity was also increased at 240 mg/kg after 2 weeks and over 120 mg/kg after 4 weeks. The results indicate that dietary Pb exposure can cause a significant stress and immune stimulation of S. schlegelii.