In this study, in order to observe the histopathological changes of liver, kidney, intestine and gills of Common Carp after using Cupper sulfate 8.5 mg/lit, Zinc sulfate 33 mg/lit, Mercuric sulfate and Cadmium cloride 10 mg/lit respectively for 3-24 hrs., the tissue from each group were sampled. Hematoxylin & Eosin staining procedure was used to reveal the histopathological changes. One of the most lesions of branches which can be occurred very clear and evidence was lamellar fusion. Hyperemia, hemorrhage, aneurism, telangiectasis , infiltration of inflammatory cells and epithelial hyperplasia of gills were observed which caused, respiratory problems. The degenerative changes in the kidney consisting of necrosis, hyaline degeneration of tubules and substitution with lymphocytes. In liver, fatty change, hyperemia, hemorrhage, hepatocellular necrosis and infiltration of lymphocytes and phagocytes were exisred. There was not any lesions in cardiac and skeletal muscle tissues.
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