title: [Effects of static magnetic field with different exposure time on the maturation of rat osteoblasts in vitro and the expression of the estrogen receptor gene].
abstract: OBJECTIVE
  To investigate the effects of static magnetic fields (SMFs) with different exposure time on the maturation of rat osteoblasts in vitro and the expression of the estrogen receptor (ER) gene.
  
  
  METHODS
  The calvarial osteoblasts were isolated from newborn rats by enzyme digestion and randomly divided into 9 groups after one passage based on the exposure time of the SMFs[0 (control), 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, and 4.0 h]. The intensity was 3.9 mT in all SMFs. Those without SMFs exposure were used as the controls. The oeteoblasts were observed under the contrast phase microscope on a daily basis. After 48 h, cell proliferation was assayed by MTT method. The osteocalcin contents were measured after exposure to SMFs for 3 d, 6 d, 9 d, and 12 d. ERΑ and ERΒ mRNA expressions were measured by real-time PCR after SMFs treatment for 0 h, 24 h, 48 h, and 72 h.
  
  
  RESULTS
  Compared with the controls, the cell proliferation was significantly enhanced in the 2.0-h, 2.5-h, and 3.0-h groups (P<0.05). After SMFs treatment for 6 d, 9 d and 12 d, the 2.5-h group had significantly higher osteocalcin content than the control group did (P<0.05). After SMFs treatment for 0 h and 72 h, elevated ERΑ mRNA expression and reduced ERΒ mRNA expression were observed.
  
  
  CONCLUSIONS
  Exposure to SMFs, regardless of exposure time, is associated with enhanced cell proliferation, increased osteocalcin contents, and altered ERΑ and ERΒ mRNA expressions in opposite directions.
authors.affiliation: Institute of Orthopaedics, Lanzhou General Hospital of Lanzhou PLA, Lanzhou, China.
authors.forename: Jia-qi
authors.initials: JQ
authors.lastname: Wang
authors.forename: Xiao-ni
authors.initials: XN
authors.lastname: Ma
authors.forename: Jian
authors.initials: J
authors.lastname: Zhou
authors.forename: Bao-feng
authors.initials: BF
authors.lastname: Ge
authors.forename: Xiao-yu
authors.initials: XY
authors.lastname: Guo
authors.forename: Ke-ming
authors.initials: KM
authors.lastname: Chen
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D060526:Magnetic Fields; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*
chemical_list: D011960:Receptors, Estrogen