Expression of mt2 and smt-B upon cadmium exposure and cold shock in zebrafish (Danio rerio).
Metallothionein-2 (mt2) and similar to metallothionein-B (smt-B) are included in the MT gene family. The objective of this study was to compare mt2 and smt-B messenger (m)RNA expressions after cadmium exposure and cold shock with whole-mount in situ hybridization in immature zebrafish (Danio rerio) and with a semi-quantitative RT-PCR in mature zebrafish. Three-day post-fertilization (dpf) larvae were treated with 0, 0.08, 0.26, and 0.89 microM cadmium for 24 and 48 h, and some larvae were challenged with a normal (28.5 degrees C) or low temperature (12 degrees C) for 12, 24, and 48 h. Results were obtained. (1) During embryonic and larval development, mt2 mRNA existed at 6 h post-fertilization (hpf), and the level rapidly increased to 24 hpf, then it gradually increased with further larval growth. smt-B was found at 12 hpf, and it also rapidly increased to 24 hpf, but remained constant during further larval development. (2) The mt2 mRNA signals and whole-body Cd contents displayed dose- and time-dependent responses after Cd exposure. After cold shock, mt2 mRNA signals also showed time-dependent expression. But smt-B mRNA signals were not appeared by either challenge. Besides, mature zebrafish were treated with 1.78 microM Cd and found that the highest levels of smt-B mRNA (smt-B/beta-actin) appeared in brain, and seems a reverse expression between smt-B mRNA and mt2 in brain after Cd exposure. Apparently, mt2 is possibly more relevant to Cd detoxification and cold shock adaptation in zebrafish larvae compared to smt-B, but smt-B might be related to certain physiological functions in neural (or brain) of mature zebrafish.
Wu
Su Mei
SM
Department of Aquatic Biosciences, National Chiayi University, Chiayi 600, Taiwan. sumei@mail.ncyu.edu.tw
Zheng
Yu Da
YD
Kuo
Chien-Hsien
CH
D000595:Amino Acid Sequence; D000818:Animals; D019256:Cadmium Chloride / Q000633:toxicity*; D003080:Cold Temperature; D004305:Dose-Response Relationship, Drug; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D017403:In Situ Hybridization; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
D012333:RNA, Messenger; D014874:Water Pollutants, Chemical; D029961:Zebrafish Proteins; D008668:Metallothionein; D019256:Cadmium Chloride