Effects of copper, cadmium and chromium cations on the freshwater fish Clarias batrachus L

The data on the effects of cations such as Cu2+, Cd2+ and Cr6+ on the changes in the biochemical parameters in a freshwater fish, Clarias batrachus L., showed an increase of the protein content in the liver, kidney, stomach, intestine, testis and ovary, and a decrease in the muscle after Cu2+ and Cd2+ treatment as compared with control data; but the Cr6+ did not cause any changes of protein concentration in the kidney and testis. The administration of Cu2+ and Cd2+ increased the concentration of free amino acids in all the fish organs, whereas the Cr6+ did not changes this concentration in the muscle. A decrease in dry weight, and an increase in tissue permeability after these treatments were recorded in all the organs studied. In general, the above biochemical parameters of the organs were affected by treatments of the above cations in the following order: Cd greater than Cu greater than Cr over control values of C. batrachus, and their effects were markedly pronounced in the liver and kidney, followed by the intestine, stomach, muscle, testis and ovary in this species.