Dynamics of metallothionein in organs of Carassius auratus under combined stresses of Cd and Zn.

Impact of combined stress of heavy metals,cadmium and zinc in water was studied on content of metallothionein(MT) in liver and kidney of Carassius auratus living therein under a given experimental condition.Results indicate that after exposure to 0.005,0.010,0.050,0.100,0.500 mg·L-1 Cd 1.0 mg·L-1 Zn,the fishes showed a similar trend of MT content in their livers and kidneys,rising-falling-rising,with a peak value appearing at the 12th hour of exposure,and ranging from(5.735±0.016) to(10.640±0.023) μg·g-1 in liver and from(8.346±0.014) to(12.990±0.031) μg·g-1 in kidney.The fishes were all higher in the groups of Cd2+ Zn2+ treatments than in the groups of Cd2+ treatments in MT content in the liver and kidney of C.auratus,indicating that the presence of Zn2+ enhanced synthesis of MT in C.auratus tissues.The content of MT in liver rose at a rate of 0.22~0.69 μg·g-1·h-1 during the first 12 hours and in kidney at a rate of 0.83~1.67 μg·g-1·h-1 during the first 6 hours.A positive relation was observed of MT contents in livers of the fish with Cd2+ concentration of the waterbody in 12 h,indicating that coexistence of Cd2+ Zn2+ may induce synthesis and expression of MT in C.auratus tissue mainly within the first 12 h.The findings of the study reveal that MT content in the liver and kidney of C.auratus can be used as a bio-indictor of extraneous heavy metal pollution.