Metallothionein Expression in Estuarine Catfish (Arius thalassinus) Kidney on Exposure to Heavy Metals (Cd, Pb, Cu and Zn) Concentration

Immunohistochemical techniques have been used to identify Metallothionein3 (MT3) expression specifically to detect MT3 levels in the kidney. The techniques employed are highly sensitive, thus allowing the detection of very low amount of proteins with the use of antibodies. The present study aimed at identifying the MT3 expressions and localizations in the kidney tissue of estuarine catfish Arius thalassinus from Kuala Gula using immunohistochemical methods. Primary mouse monoclonal anti-MT3 (1F11), primary antibody (1:2000), secondary antibody and Goat anti-mouse IgG2 (1:2000) were used. MT3 bands were detected using (Santa Cruz kit USA method). Heavy metals (Cd, Pb, Zn and Cu) were determined using aqua regia’s methods followed by analyses with AAS. The results showed high expressions of Metallothionein3 (MT3) with an increasing concentration of heavy metals. Large catfish A. thalassinus had higher accumulation of heavy metals concentrations therefore, exhibiting higher expressions than smaller sized fish. The concentration of heavy metals in fishes were: Zn (284.00 ±29.7, 259.32± 23.2 and 240.90±20.3 μg/g-1 d.w), Cu (7.00±1.7, 6.90±1.3 and 5.60±1.8 μg/g-1 d.w), Pb (66.80±10.8, 35.31±6.4 and 26.02±6.9 μg/g-1 d.w) and Cd (1.32 ± 0.12, 1.19 ±0.12 and 1.20± 0.09 μg/g-1 d.w) in large, medium and small fish respectively. The results of this study suggests it suitability as biomarker candidate for pollution assessment in the aquatic environment. The different MT3 expressions in different sized fish and different polluted places showed the potential use of MT3 as biomonitoring biomarker for heavy metals exposure in an aquatic environment.