Toxicity of Heavy Metals on Fish at Jeddah Coast KSA: Metallothionein Expression as a Biomarker and Histopathological Study on Liver and Gills

Abstract

5 Abstract: Metal pollution may damage marine organisms at the cellular level and possibly affect the ecological balance. Metallothionein (MT) is a low molecular weight protein that binds heavy metals in marine organisms, therefore, it is considered as biomarker of heavy metal pollution in aquatic environments. In this study, the expression of MT production and histopathological changes in Sleek Unicorn fish (Naso hexacanthus) was examined due to heavy metal pollution. Fish were collected from five sampling areas and two potentially non-contaminated (Control) areas, over the coast Jeddah on Red Sea. Cd, Cu, Zn and Pb concentrations were measured at studied areas. Liver and gills from samples were used for, histopathological, histomorphometrical examinations and MT-gene expression assays. Histopathological examination of the liver revealed hepatocytes vacuolation, cellular swelling, nuclear degeneration and congestion of blood vessels. Pathological changes of gills exhibit secondary lamellar disorganization, rupture in lamellar epithelium and epithelial lifting. Morphometric measurements showed significant decrease in both secondary lamella length (SLL), width (SLW) and interlamellar distance (ILD) in fish from contaminated areas. Gene expression of MT, resulted in significant increase in response to metal pollution. In conclusion, in this study using MT as biomarker revealed clear metal pollution in the studied areas of Red Sea near Jeddah coast which was proven by the histopathological assessment. Therefore, the problem of metal pollution is considered among the most serious once that face mankind in the twenty-one century. It is supposed to be one of the greatest national health problems with referring to peoples eating sea foods in KSA, it require special and intense effort at all level individual, groups, national, and international.