Expression of metallothionein cDNA in a freshwater crab, Sinopotamon yangtsekiense, exposed to cadmium.

This paper aims at evaluating the induction of metallothionein (MT) synthesis in gills, heart and hepatopancreas of a freshwater crab, Sinopotamon yangtsekiense. Crabs were exposed to different cadmium concentrations (from 0 to 5 mg/L) from 24 to 96 h. The amount of cadmium (Cd) accumulated in gills, heart and hepatopancreas of the crab showed an increase with an increase in the treatment concentration. Furthermore, the amount of Cd accumulated in these tissues showed an increase with an increase in duration. On the other hand, MT and β-actin genes were amplified using reverse transcription PCR (RT-PCR). Metallothionein gene expression induced by Cd was analyzed using real-time quantitative polymerase chain reaction. Its expression levels were correlated to duration time and increased with cadmium concentrations in water, whilst β-actin was expressed at a relatively constant level. The MT transcript levels in gills and hepatopancreas were higher than that in heart. Furthermore, the MT mRNA expression was not time dependent, and no relationship with Cd accumulation followed the time course of treatment at the same dose Cd treatment. But the clear dose response of MT to cadmium exposure of S. yangtsekiense is a proof of the feasibility of MT as a biomarker for testing cadmium pollution.