| Polychlorinated Biphenyls (PCBs) existed in water widely for its characters which were difficult to decompose and to portative by the organism. The quantity of PCBs enriched in the body of fish by food chain,so it was harm to fish and human being especially after the Three Gorge Reservoir Region coming into existence. Furthermore, the intensity and scale being would enormously increase because of the pollution of PCBs, and the self-purification of water body would obviously weaken and the fish ecosystem would be in danger. So it was necessary to study deeply on the toxicity of PCBs to fish.Taking the special carnivorous fish, south catfish (Silurus meridionalis Chen) and graminivorous fish, grass carp (Ctenopharyngodon idellus (Cuvier et Valenciennes)) as experimental materials, we studied the effects of PCBs exposured to the structure of liver, gill, kidney of south catfish and the correlative physiology factors of south catfish and grass carp by acute toxicity experiment. The results are as follows.In the process of PCBs exposure to water 30d in the concentration of 0. 1μg/l, 0.5μg/l, 2.5μg/l, 10μg/l, 20μg/l, 40μg/l, 60μg/l, the south catfish traveled slowly and lost its appetite and there were mucilage increasing obviously in the face of body and gill filament which showed wine. From the whole experimental process, all of the concentrations of PCBs during the experimental stage was not fatal to catfish.The results of histology after exposing the south catfish to PCBs 1d, 3d, 7d, 15d, 20d and 30d indicated that all the concentrations in the above experiment of PCBs were caused damage to the liver, kidney and gill of catfish. In the 7d, there were significant difference of the liver cell and the karyon area, and the long and short diameter compare to control group; after 15d and 25d, the liver cell area and the long diameter reached to significant difference level only in high concentration of exposure to the PCBs compare to control group. Under the PCBs concentration of 60μg/l, the liver cell and the karyon area, and the long and short diameter are all smaller groups are smaller than control group. In the same time exposure to the PCBs, there were no difference among the liver cell and the karyon area, and the long and short diameter. After exposure to the PCBs, the kidney's PI(the first proximal segement) separated from the tissue around it,and the epithelia in the kidney tube showed strong indulge in acidity, the karyon became shuttle-like, and characteristics were more evident with the exposure concentration increased. The PI's cell and karyon area and long diameter of cell and karyon were significantly different from control group, but the cell and karyon were smaller than control group. According to transmission electron microscope observation after exposure to PCBs 1d, 3d, 7d, 15d, 20d, 30d, the membrane of the liver had broken in some degree, and the quantity of lysosome increased and the mitochondrion augment and ridge became unconspicuous or disappear.Part of the karyon of Kuffer's cell became distorted and been pushed to brim of cell.There was Lipofuscin in the cytoplasm.The volume of PI's epithelia became more bigger,and its karyon concentrated and short diameter became smaller.The epithelia of gill filament became fragmentary and there were fragment of epidermis.The supporting cell abnormity, and chloride cell was increased obviously.The gill structure of exposured group was injured significantly.The enzyme activity in the liver of Silurus meridionalis and Ctenopharyngodon idella changed with the time of exposure to the PCBs: the activity of CAT was significantly restrained in lower concentration of PCBs and the restrain was more obviously according to extend of exposing time. But the activity of CAT increased in 24h, then declined, and had significant difference compare to the control group which indicated that the activity of CAT was restrained significantly and with the time protract of exposure to the PCBs, the activity of CAT was enhanced. With the time increasing, the activity of GPT of Silurus meridionalis and Ctenopharyngodon idella were enhanced significantly, there was low-grade SOD inducement in the Ctenopharyngodon idella liver during the experiment. The activity of GSH-PX increased in early stage, then declined, and durative increased. As the exposure time prolonged, the activity of GSH-PX was restrained in 125μg/l and the activity of liver GSH-PX was increased under 125μg/l.Though Silurus meridionalis and Ctenopharyngodon idella displayed sensitivity to PCBs, the liver, kidney and gill etc. were damaged and some enzyme in the liver was changed, so the symptom was different. The study indicated that the poisonous mechanism of PCBs was very complex and more and further study were necessary.
|
PDF Full Text Request