Effects of cadmium on carbohydrate and protein metabolisms in the freshwater crab Sinopotamon yangtsekiense.

The physiological impact of Cd(2+) on Sinopotamon yangtsekiense was evaluated through changes of selected parameters considered as key elements of carbohydrate and protein metabolisms. Crab were exposed to 0.725, 1.45, 2.9mg·L(-1) Cd(2+) for 7, 14 and 21 days. A time- and/or concentration- dependent decrease in muscle glycogen and increase in LDH activity suggested that glycolysis was accelerated during the treatments. Increased protease activity, lowering of FAA and the initially increased and subsequently decreased aminotransferase activities suggest an enhanced protein mobilization during early Cd(2+) exposure followed by a metabolic impairment during late exposure. Decreased hemolymph glucose level was observed in the crabs treated with 2.9mg·L(-1) Cd(2+) for 21d, suggesting an impaired gluconeogenesis. Ammonia level barely changed during the 14d Cd(2+) exposure most likely due to the increased urea and glutamine production; After 1.45 and 2.9mg·L(-1) Cd(2+) treatment for 21d, ammonia was observed increased followed by an exclusive increase in glutamine. Taken together, our results indicate that carbohydrate and protein are mobilized to a varying degree as a compensatory metabolism to response to the energy stress during acute Cd(2+) exposure. As the time lapsed, some symptoms on metabolism obstacle reflect the toxic effect of sublethal Cd(2+).