| The environmental biotechniques ,atom absorption spectrum techniques were used to investigate the effect of cadmium accumulation and distribution under cadmium on the sublethal concentration and the physiological toxicity caused by cadmium. The significance of this research is that to understand the effects of sublethal metal toxicity on the grass carp and how such effects could be set up as molecular biomarkers to indicate the exposure of fish to low cadmium concentrations. The research findings can be used as a scientific basis for making standards and law to prevent or eliminate the hazards of metals to the aquatic ecosystem.The result of the acute toxicity tests of cadmium ,copper and zinc to Grass Carp showed that the semi-lethal concentration (LCso) of cadmium on 24, 48 ,96hours of Grass Carp fingerling were 5.86mg/l, 4.53 mg/1, 3.49 mg/1; the semi-lethal concentration (LCso) of zinc on 24 ,48, 96hours of Grass Carp fingerling was 8.18 mg/1, 7.36 mg/1, 5.73 mg/1; the semi-lethal concentration (LCso) of copper on 24,48,96 hours of Grass Carp fingerling was 0.31 mg/1, 0.21 mg/1 , 0.16 mg/1. The safe concentration to cadmim and zinc and copper are 0.81 mg/1,1.79 mg/1, 0.03 mg/1. The cadmium and zinc and copper have obvious toxicities to Grass Carp ,their order is Cu>Cd>Zn.The joint action of cadmium and zinc were studied .According to the addictive index method of Marking , the joint toxicity on 24h and 48h are antagonism .The join toxicity on 96h is synergism action. The results on the joint action of cadmium and copper showed that the joint toxicity on 24h and 48h and 96h are synergism .And the longer of the exposure time ,the stronger effect is .The liver and gill tissues of Grass Carp were treated at different Cadmium levels(1.10mg/l, 2.19mg/l and 4.37mg/l)for 6h, 24h, 72h, The SOD activity of liver and gill tissues decreased significant in high cadmium groups ,compared with the controls. On the 6h, the SOD activity of liver and gill tissues raised significantly in lowSOD IP ATPase ftcadmium groups .The SOD of the gill tissue was more susceptive to cadmium. At the cadmium concentration of 2.19mg/l and 4.37mg/l ,for 72h, the Na+-K+-ATPase activity of kidney tissues were decreased very significantly. The higher of the concentration of cadmium or the longer of the exposure the more the enzymic activity was decreased. The Na+-K+-ATPase activity of gill tissues were decreased but not significantly at the low concentratioin of cadmium. At the concentration of 4.365mg/l for 72 h, the Na+-K+-ATPase activity of gill tissues decreased significantly.The Na+-K +-ATPase activity of kedney was more suspceptive to cadmium .The experimental carps were raised with ICd2+0.69mg/L ,1.10mg/L and 1.75mg/L respectively. The carps were sampled after raising 24h,48h,72h and 96h.,and separated into scale viscera, gill and fresh. The distributive and accumulative rules of cadmium are studied, with measuring the radioactivity .The results showed that Cd was absorbed rapidly by carp via gill and alimentary canal from water ,and distributed into al parts of the body ,mainly in soft tissue with blood circulation . The results show that the contents of cadmium in Grass Carp tissues are visccra>gill>scales>fresh. The study shows that Cd concentration in the viscera tissue gradually increased during exposure time. There was a linear relationship between the specific activity of Cd in viscera and the carp s raising time in Cd water . Cd concentration in the gill and scales and fresh tissue gradually increased till a maximum ,but gradually declined .SOD isozymes in liver and kidney were analysed by level slab polyacrytamide gel electrophoresis .The isozymic phenotypes of SOD had evident difference between the tow tissue .The SOD isozyme band of the tow tissue have changed in varing degree after exposure to cadmium.
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