الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Living organisms’ posses the capability to tolerate and resist the damaging effect of heavy metals through the formation of certain kind of binding proteins known as Metallothionein. Metallothionein has the power to bind with the heavy metals and sequester them inside the tissue up to certain limit of the concentration of heavy metals in organs. This study is carried out on a sample of catfish obtained from Manzala Lake are divided into 3 groups according to their sizes: small, medium and large. It is found that there is a positive correlation between length and weight of catfish. Cadmium, zinc and copper are determined in the water and Cd was exceeded the permissible limit. There is a positive correlation between catfish sizes and the accumulation of heavy metals (Cd, Zn and Cu) in catfish. There is a significant increase in malondialdehyde concentration by increase in catfish size. The activity of superoxide dismutase, catalase and glutathione S transferase is increased by the increase in catfish size, so they are considered a good biomarkers for heavy metal pollution Total lipids, low density lipoprotein- cholesterol, triacylglycerol and total cholesterol are increased by the increase the size of catfish, while high density lipoprotein- cholesterol is decreased by the increase in catfish size. Metallothionein protein concentration is directly proportional with catfish size and also is directly proportional with the concentration of heavy metals in catfish organs. Metallothionein gene expression is performed by using reverse transcriptase polymerase chain reaction. Metallothionein gene is expressed in the liver of large size catfish, which is also showed a high concentration of Metallothionein protein, so Metallothionein gene and protein expression is a good biomarker for heavy metal pollution in catfish from Manzala Lake, especially Metallothionein protein because it could detect low concentrations of Metallothionein by nanomoles.