Bioaccumulation, alterations of metallothionein, and antioxidant enzymes in the mullet Mugil cephalus exposed to hexavalent chromium

A laboratory experiment was conducted to determine hexavalent chromium (Cr) accumulation in the mullet and investigate Cr toxicity using a panel of biomarkers including metallothioneins (MTs), glutathione (GSH), glutathione S-transferase (GST), and superoxide dismutases (SODs) for 4 weeks. Cr bioaccumulation in all tissues, except muscle, was consistently timeand dose-dependent. The accumulation of Cr for 4-week exposures was in the following order: kidney ≈ liver > intestine ≈ gill > spleen > muscle. Compared with the control, Cr bioaccumulation was increased in ≥200 μg L groups (P < 0.05). An independent relation was observed between accumulation factors (AFs) and exposure concentration. But AFs increased with exposure time. In the liver and gill, GST and SOD differed from the control at a high Cr concentration at 2 and 4 weeks (P < 0.05). This study indicated that the gills were as sensitive as the liver to Cr toxicity. However, the latter appeared to influence largely on the organism’s adaptive response to Cr, since Cr may elevate GSH and MT levels by enhancing the hepatic uptake of metal in the mullet.