Time kinetic study of metallothionein mRNA expression due to cadmium exposure in freshwater murrel, Channa punctata (Bloch)

Metallothionein (MT) is a low molecular weight, cysteine-rich protein whose cysteinyl residues are involved in the metal coordination. MT induction and the associated increase in binding of metals by MT have been used as prima facie evidence for functions in metal detoxification, sequestration and storage. A quantitative real-time reverse-transcriptase polymerase chain reaction (q-RT-PCR) study was carried out for 14 days using freshwater murrel, Channa punctata (Bloch). After exposure to 3.74 mg L⁻¹ waterborne cadmium, the MT gene was over expressed in liver during the first 8 hours of contamination but repressed from day 1 to 14. In contaminated kidney, this gene was repressed the first day and up-regulated on day 14. In contaminated gills, the MT gene expression remained at the basal level at all the time points. The study indicates that MT mRNA expression was found to be tissue specific with respect to duration of the metal exposure.