الفهرس 
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Abstract
The present study used Nile tilapia (Oreochromis niloticus) as an biological marker to revealed the concentrations of some heavy metals (Cu, Pb and Cd) in water, gills and muscles of fish collected from four sites in Egypt {Maryuot Lake, Manzala Lake and the River Nile (Mansura)} which are polluted by industrial effluents, waste municipal and agricultural drainage water that is discharged directly into them in addition to Ismailia Canal (Abbassa) as control. Analysis of water samples showed that Abassa site was the lowest concentration of copper, cadmium and lead (0.18, 0.0 and 0.19 ppm, respectively) while, Manzala Lake site showed the highest concentration (16.38, 2.87 and 10.1, respectively) and heavy metals in the water samples of Abassa site were within the permissible limits. Abassa site showed the lowest concentrations of the three heavy metals in gill and muscle while, Manzala Lake site indicated the highest concentrations. Copper and cadmium in gill and muscle samples of Abassa site and muscle samples of Mansoura site were within the permissible limits.
The results of this study confirmed the usefulness of the erythrocyte micronucleus as a powerful monitoring tool for detecting genotoxic agents in an aquatic environment . The frequencies of MN were significant in gills blood erythrocytes of Nile tilapia from all sites compared to control. Manzala and Maryout had high frequency of erythrocytes with MN(6.46 ,4.32 respectively) compared to controls
Polyacrylamid gel electrophoresis was used to study protein banding pattern variation in tested fish and was showed variation in number of phenotypic bands and the variation between and within each site was clear. Protein locus (55 KDa) in 90% of Mansoura samples and also protein locus (32KDa) in all samples were missed compared to control Site. Maryuot Lake samples demonstrated loss of protein loci (55 and 60 KDa) in 100% of samples and appeared a new protein locus (163 KDa) with ratio of 75%. Manzalla samples compared with control were missed protein locus (60 KDa) in all samples and appeared a new protein locus (163 KDa) in 25% of samples. Appear of a new protein locus (163 KDa) in Maryuot and Manzalla Lakes considered as a resistance protein for pollution.