title: Metallothionein and superoxide dismutase responses to sublethal cadmium exposure in the clam Mactra veneriformis.
abstract: The objective of this study was to identify the relationship between cadmium (Cd) and stress responses in the clam Mactra veneriformis. Metallothionein (MT) and Cu-Zn superoxide dismutase (SOD) cDNAs from the clam were isolated and characterized. The full-length cDNA of MvMT and MvSOD contained 830 and 689 nucleotides encoding 59 and 159 amino acids, respectively. Multiple alignments indicated that deduced amino acid sequences of MvMT and MvSOD shared high homology with MT and SOD sequences of other mollusks. Clams were exposed to 0, 50, 100, and 200microg/L Cd for 21days. The mRNA transcripts of the two genes, MT protein content and SOD activity in the digestive gland were examined. Cd treatment significantly elevated MvMT and MvSOD mRNA expression in a dose-dependent manner and MT protein level in a dose- and time-dependent manner. SOD activity significantly increased at the start of Cd exposure, then decreased and finally returned to the normal level. These results indicate that MT and SOD play an important role in maintaining cellular metabolism homeostasis and protecting M. veneriformis from Cd toxicity. MT and SOD could be used as biomarkers of Cd pollution in aquatic environment for the studied species.
authors.affiliation: Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Fang
authors.forename: Hongsheng
authors.initials: H
authors.lastname: Yang
authors.forename: Tianming
authors.initials: T
authors.lastname: Wang
authors.forename: Baozhong
authors.initials: B
authors.lastname: Liu
authors.forename: Heling
authors.initials: H
authors.lastname: Zhao
authors.forename: Muyan
authors.initials: M
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D049872:Bivalvia / Q000502:physiology*; D002104:Cadmium / Q000633:toxicity*; D003001:Cloning, Molecular; D016384:Consensus Sequence; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D008668:Metallothionein / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013482:Superoxide Dismutase / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D014874:Water Pollutants, Chemical; D002104:Cadmium; D008668:Metallothionein; D013482:Superoxide Dismutase