Effects of cadmium and benzo(a)pyrene on the immune system, gill ATPase and EROD activity of European sea bass Dicentrarchus labrax

Abstract

Juvenile European sea bass ( Dicentrarchus labrax) were exposed to cadmium (40 μg l −1) for 15 days and then injected with benzo(a)pyrene (BaP) (20 mg kg −1) for 14 h. In the immune system, phagocytosis was reduced both in spleen and kidney macrophages after cadmiumexposure and/or BaP injection, with a synergistic effect of the combined pollutants. Spleen and kidney respiratory burst (measured by hydrogen peroxide production) showed different patterns of response to cadmium and BaP. Cadmium exposure had no effect on spleen macrophages, although BaP totally inhibited the respiratory burst. In kidney macrophages, cadmiumexposure and BaP injection resulted in enhanced hydrogen peroxide production. After BaP injection, hepatic micrososomal 7-ethoxyresorufin- O-deethylase (EROD) activity was increased 21-fold compared with the control, but the induction was even greater (34.5 times compared with the control) in cadmium-exposed fish. However, although an induction (11 times compared to the control) occurred after cadmium exposure the effects of both pollutants were not synergistic (not additional). No perturbation of the gill Na +/K +-ATPase activity was observed in cadmium-exposed fish, but the activity was increased in BaP-injected fish. The role of BaP metabolites and cadmium as both direct effectors and indirect stressors, responsible for the changes in the immune system and gill and liver biochemistry of the fish are discussed.