title: Cadmium sensitivity, uptake, subcellular distribution and thiol induction in a marine diatom: Recovery from cadmium exposure.
abstract: Studies in the recovery from metal stress and the tolerance development to metal exposure of aquatic organisms are important for the understanding of epidemic pollution. In this study, the responses of a marine diatom, Thalassiosira nordenskioeldii, following recovery from environmental cadmium (Cd) stress were investigated. The diatoms were exposed to different concentrations of Cd for 7 days, and were then allowed different periods of time to recover. The Cd sensitivity increased after recovery from Cd stress, followed by a gradual restoration. The extent of restoration depended on both the recovery time and the environmental Cd stress during the exposure period. A complete restoration of Cd tolerance proved to be impossible for cells pre-exposed to High-Cd. The Cd cellular burden and subcellular Cd concentration decreased to the control level within the first day of recovery, indicating that the elevated sensitivity may have been due to the accumulation of functional damage caused by Cd exposure instead of a result of physical Cd accumulation. The rapid change in phytochelatins (PC) to both the increase in and the withdrawal of environmental Cd stress made it a good quantitative bioindicator of environmental Cd contamination. However, the relationships between Cd distribution in the metal sensitive fraction (MSF-Cd) or intracellular Cd to thiol ratio (intra-Cd/PC-SH) and the relative change in the median inhibition [Cd(2+)] ([Cd(2+)]-based-IC(50), i.e., Cd sensitivity) differed for the various exposure and recovery periods tested. Our study suggests that more attention should be given to the recovery of aquatic organisms from episodic metal exposure.
authors.affiliation: State Key Laboratory in Marine Pollution, Section of Marine Ecology and Biotechnology, Division of Life Science, The Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Meng-Jiao
authors.initials: MJ
authors.lastname: Wang
authors.forename: Wen-Xiong
authors.initials: WX
authors.lastname: Wang
mesh_terms: D002104:Cadmium / Q000378:metabolism / Q000493:pharmacokinetics* / Q000633:toxicity*; D017377:Diatoms / Q000187:drug effects* / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D054811:Phytochelatins / Q000096:biosynthesis / Q000378:metabolism; D010940:Plant Proteins / Q000096:biosynthesis; D013347:Subcellular Fractions; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000493:pharmacokinetics / Q000633:toxicity
chemical_list: D010940:Plant Proteins; D013438:Sulfhydryl Compounds; D014874:Water Pollutants, Chemical; D002104:Cadmium; D054811:Phytochelatins; D005978:Glutathione