World Journal of Fish and Marine Sciences 2 (3): 174-185, 2010 ISSN 2078-4589 © IDOSI Publications, 2010 Corresponding Author: Metwally Montaser, Center for Genetic Engineering, Al-Azhar University, Cairo, Egypt, Current address: Department of Biotechnology, Faculty of Science, Taif University, 888 Hawia, Taif, KSA 174 Toxicity of Heavy Metals on Fish at Jeddah Coast KSA: Metallothionein Expression as a Biomarker and Histopathological Study on Liver and Gills Metwally Montaser, Magdy E. Mahfouz, Samir A.M. El-Shazly, 1,2 3 1,4 Gamal H. Abdel-Rahman and Sayed Bakry 5 2 Department of Biotechnology, Faculty of Science, Taif University, 888 Hawia, Taif, KSA 1 Center for Genetic Engineering, Al-Azhar University, Cairo, Egypt 2 Faculty of Science, Kafrelsheikh University, Kafrelsheikh, Egypt 3 Department of Biochemistry, Faculty of Veterinary Medicine, Kafrelsheikh, University 4 Faculty of Science, Assiut University, Assiut, Egypt 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. Key words: Metallothionein %Biomarker %Metal pollution %Histopathology %Red Sea INTRODUCTION as heavy metals which find their way into different water Industrial development in the developing and [2]. Petroleum products are one of the most relevant developed countries has resulted in heavy metal pollutants to aquatic ecotoxicology. Exposure to crude oil contamination of local waters. Metal pollution may and derivatives can induce a variety of toxic symptoms in damage marine organisms at the cellular level and experimental animals. Petroleum hydrocarbons can act as possibly affect the ecological balance. Exposure and a mediator in free radical generation in fish [3]. ingestion of polluted marine organisms as sea foods can Jeddah is a major city with a population of over cause health problems in people and animals including 2.6 million and an area 1,200 km2. Samples of the Red Sea neurological and reproductive problems [1]. Chemicals of water were collected from 24 important locations near industrial effluents and products of ships and boats such Jeddah and analyzed in the laboratory for various water systems can produce toxic effects in aquatic organisms