title: Mercury, cadmium, and arsenite enhance heat shock protein synthesis in chick embryos prior to embryotoxicity.
abstract: BACKGROUND
  Cells respond to adverse environmental stimuli by enhancing the expression of specific genes, the products of which include a suite of proteins known as heat shock proteins (hsps), a response often attributed to cellular protection.
  
  
  METHODS
  In this study, we characterized alterations in hsp expression in chick embryos (Hamburger-Hamilton stage 17, 72 h) exposed in ovo to arsenite (As), mercury (Hg), and cadmium (Cd), known developmental toxicants. Embryos were incubated for 2 h following exposure to 3, 10, 30, or 100 nmol metal, or for 2, 4, 12, or 24 h following treatment with 10 nmol metal.
  
  
  RESULTS
  An enhanced de novo synthesis of 24-, 70-, and 90-kD, 70- and 90-kD, and 70-kD proteins was observed with As, Hg, and Cd treatments, respectively. These responses were transient; apparent rates of protein synthesis were maximal 2-4 h after exposure and returned to control rates by 24 h. Actinomycin D experiments demonstrated that arsenite-induced expression of these proteins is transcriptionally regulated. Immunoblotting experiments identified the 24-, 70-, and 90-kD proteins as the heat shock proteins hsp24, hsp70, and hsp90, respectively. Exposure duration-related abnormalities were noted in the neural tube with all metals and in the ganglia and somites with Cd and As. Retina, allantois, and limb defects were specific to Cd-treated embryos, and branchial arch defects were specific to As-treated embryos.
  
  
  CONCLUSIONS
  The data support metal-induced developmental abnormalities, which are preceded by synthesis of stress proteins.
authors.affiliation: Center for Devices and Radiological Health, Food and Drug Administration, Rockville, MD 20857, USA.
authors.forename: Andriana D
authors.initials: AD
authors.lastname: Papaconstantinou
authors.forename: Ken M
authors.initials: KM
authors.lastname: Brown
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Noren
authors.forename: Terence
authors.initials: T
authors.lastname: McAlister
authors.forename: Benjamin R
authors.initials: BR
authors.lastname: Fisher
authors.forename: Peter L
authors.initials: PL
authors.lastname: Goering
mesh_terms: D000818:Animals; D018053:Arsenites / Q000494:pharmacology*; D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology*; D002642:Chick Embryo; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004622:Embryo, Mammalian / Q000187:drug effects*; D004625:Embryo, Nonmammalian; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D015151:Immunoblotting; D007150:Immunohistochemistry; D008628:Mercury / Q000494:pharmacology*; D014176:Protein Biosynthesis; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D018053:Arsenites; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D002104:Cadmium; D003609:Dactinomycin; D008628:Mercury; C015001:arsenite