title: Oxidative stress, endocrine disruption, and malformation of Bufo gargarizans embryo exposed to sub-lethal cadmium concentrations.
abstract: Thyroid hormone (TH) is critical for vertebrate postembryonic development as well as embryonic development. Chinese toad (Bufo gargarizans) embryos were exposed to different concentrations of cadmium (5, 50, 100, 200 and 500μg Cd L-1) for 7days. Malformations were monitored daily, and growth and development of embryos were measured at day 4 and 7, and type 2 and 3 iodothyronine deiodinase (Dio2 and Dio3), thyroid hormone receptors (TRα and TRβ) mRNA levels were also measured to assess disruption of TH synthesis. In addition, superoxide dismutase (SOD), glutathione peroxidase (GPx) and heat shock proteins (HSPs) mRNA expression were examined to evaluate the ability of scavenging ROS. Our results demonstrated a bimodal inhibitory effect of Cd on the embryo growth and development of Bufo gargarizans. Reduced mean stage, total length and weight were observed at 5, 50, 200 and 500, but not at 100μg Cd L-1. Embryos malformation occurred in all cadmium treatments. Morphological abnormalities of embryos are characterized by axial flexures, abdominal edema, stunted growth and fin flexure. Real-time PCR results show that exposure to cadmium down-regulated TRα and Dio3 mRNA expression and up-regulated Dio2 mRNA level. SOD and GPx mRNA expression was significantly up-regulated after cadmium exposure. We concluded that cadmium could change mRNA expression of TRα, Dio2 and Dio3 leading the inhibition of growth and development of B. gargarizans embryo, which suggests that cadmium might have the endocrine-disrupting effect in embryos. Moreover, the reduced ability of scavenging ROS induced by cadmium might be responsible for the teratogenic effects of cadmium.
authors.affiliation: College of Life Science, Shaanxi Normal University, Xi'an 710119, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Wu
authors.affiliation: College of Life Science, Shaanxi Normal University, Xi'an 710119, China.
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: School of Environmental Science and Engineering, Chang'an University, Xi'an 710054, China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Xi'an 710062, China.
authors.forename: Lihong
authors.initials: L
authors.lastname: Chai
authors.affiliation: College of Life Science, Shaanxi Normal University, Xi'an 710119, China. Electronic address: hongyuanwang@snnu.edu.cn.
authors.forename: Hongyuan
authors.initials: H
authors.lastname: Wang
mesh_terms: D000818:Animals; D002025:Bufonidae / Q000002:abnormalities / Q000378:metabolism; D002104:Cadmium / Q000633:toxicity*; D004625:Embryo, Nonmammalian / Q000187:drug effects; D047108:Embryonic Development / Q000187:drug effects; D052244:Endocrine Disruptors / Q000633:toxicity*; D005979:Glutathione Peroxidase / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics; D007453:Iodide Peroxidase / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000235:genetics; D013482:Superoxide Dismutase / Q000235:genetics; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D000097564:Iodothyronine Deiodinase Type II
chemical_list: D002104:Cadmium; D052244:Endocrine Disruptors; D005979:Glutathione Peroxidase; D006360:Heat-Shock Proteins; D007453:Iodide Peroxidase; D012333:RNA, Messenger; D011988:Receptors, Thyroid Hormone; D013482:Superoxide Dismutase; D014874:Water Pollutants, Chemical; D000097564:Iodothyronine Deiodinase Type II; C117274:iodothyronine deiodinase type III
keywords: Bufo gargarizans; Cadmium; Endocrine disruption; Malformation; Oxidative stress