Ng T Y-T, Rainbow P S, Amiard-Triquet C, Amiard J C, Wang W-X
Department of Biology, The Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong, China.
Aquat Toxicol. 2007 Aug 30;84(2):153-61. doi: 10.1016/j.aquatox.2007.01.010. Epub 2007 Jun 16.
We examined the relationship between Cd kinetics (uptake from solution and diet, and efflux), metallothionein turnover, and changes in the cytosolic distribution of accumulated Cd between protein fractions in the green mussel Perna viridis. We pre-exposed the mussels to 5, 20, 50 and 200 microg l(-1) of Cd for 1 week and determined the biokinetics of Cd uptake and efflux in the mussels. The dietary assimilation efficiency of Cd increased by 2 times following exposure to 20-200 microg l(-1) Cd, but the dissolved uptake rate was unchanged by pre-exposure to any Cd concentrations. The efflux rate of Cd was also similar among control and Cd pre-exposed mussels. The cytosolic distribution of Cd in the mussels that had been exposed to dissolved Cd, showed that besides metallothionein (7000 - 20,000 Da), high molecular weight proteins (>20,000 Da) were important for Cd binding and depuration. In general, the Cd pre-exposed mussels had higher metallothionein turnover with a higher metallothionein synthesis rate, but similar metallothionein breakdown rates as the control mussels. Metallothionein synthesis rate was correlated to the dietary assimilation of Cd, whereas metallothionein breakdown and Cd efflux rate were independent of each other. This study provides important new information for the role of metallothionein turnover on Cd kinetics in an aquatic invertebrate.
我们研究了翡翠贻贝（Perna viridis）中镉的动力学（从溶液和食物中的摄取以及外排）、金属硫蛋白的周转以及积累的镉在蛋白质组分之间的胞质分布变化之间的关系。我们将贻贝预先暴露于5、20、50和200微克/升的镉中1周，并测定了贻贝中镉摄取和外排的生物动力学。暴露于20 - 200微克/升的镉后，镉的食物同化效率提高了2倍，但预先暴露于任何镉浓度下，溶解摄取率均未改变。对照贻贝和预先暴露于镉的贻贝中镉的外排率也相似。暴露于溶解镉的贻贝中镉的胞质分布表明，除了金属硫蛋白（7000 - 20,000道尔顿）外，高分子量蛋白质（>20,000道尔顿）对于镉的结合和净化也很重要。一般来说，预先暴露于镉的贻贝具有较高的金属硫蛋白周转和较高的金属硫蛋白合成速率，但与对照贻贝的金属硫蛋白分解速率相似。金属硫蛋白合成速率与镉的食物同化相关，而金属硫蛋白分解和镉外排速率相互独立。这项研究为金属硫蛋白周转在水生无脊椎动物镉动力学中的作用提供了重要的新信息。
