Metallothionein - A potential biomarker to assess the metal contamination in marine fishes

In this review, the fish Metallothionein (MT) is broadly discussed in relation to their utilization as a biomarker to assess the heavy metal contamination in marine ecosystem. Heavy metals are the main marine pollutants whose bioaccumulation in fishes results in deleterious effects on physiology, biochemistry and behavior. To assess the health status of fishes, an early determination of metal levels along with a biomarker like MT will help us to understand the bioavailability and toxicity of the metals. MTs constitute a family of low-molecular-weight, cysteine-rich proteins functioning in the regulation of essential metals and detoxification of both essential and nonessential metals. Since 1980, MT has been the useful tool for toxicity assessment of metals before sub lethal and lethal damage to organisms because of quick induction of MTs as metals enter the tissue. Various studies conducted on the induction, regulation and estimation of the MT by the metals showed that many variables such as sexual maturity, age, tissue type, metal type, route of exposure, changes in the environmental conditions of the living habitat of the organisms under study and presence of exogenous and endogenous substances do create fluctuations in the level of MT. Keeping in view of the above factors, this review attempts to understand the effectiveness of this biomarker in assessing the health status of the fishes.